Year 5 Place Value to 1,000,000: worked examples and questions with answers
By the end of this chapter you will be able to
- Read, write and partition numbers up to 1,000,000 and say the value of every digit
- Order and compare numbers up to 1,000,000 and use the signs < and >
- Count on and back in 10s, 100s, 1,000s, 10,000s and 100,000s from any number, including missing numbers in a sequence
- Use negative numbers in real life (temperatures, depths and bank balances) and count through zero
- Round numbers to the nearest 10, 100, 1,000, 10,000 and 100,000 and use rounding to estimate
- Read and write Roman numerals up to 1,000 and read years such as MCMXCIX and MMXXVI
- Solve problems and puzzles that use place value, ordering, rounding and negative numbers
You should already know
- Place value of numbers up to 10,000
- Counting in steps of 1,000 and finding 1,000 more or less
- Rounding to the nearest 10, 100 and 1,000
- Counting back through zero (temperatures)
- Roman numerals to 100
Where this leads
- Adding and subtracting numbers with more than 4 digits (Chapter 2)
- Multiplying and dividing by 10, 100 and 1,000 (Chapters 4 and 5)
- Decimals and place value to three decimal places (Chapter 7)
- Place value to 10,000,000 and calculating across zero in Year 6
National Curriculum for England, Key Stage 2 mathematics, Year 5. Content: Read, write, order and compare numbers to at least 1,000,000 and know the value of each digit, Count forwards or backwards in steps of powers of 10 for any given number up to 1,000,000, Interpret negative numbers in context; count forwards and backwards through zero, Round any number up to 1,000,000 to the nearest 10, 100, 1,000, 10,000 and 100,000, Solve number and practical problems that involve all of the above, Read Roman numerals to 1,000 (M) and recognise years written in Roman numerals.
- 1.1 Reading and writing numbers to 1,000,000: Worksheet (PDF) · Answers (PDF) · lesson page
- 1.2 Comparing and ordering numbers to 1,000,000: Worksheet (PDF) · Answers (PDF) · lesson page
- 1.3 Counting in steps of 10, 100, 1,000, 10,000 and 100,000: Worksheet (PDF) · Answers (PDF) · lesson page
- 1.4 Negative numbers: temperatures, depths and bank balances: Worksheet (PDF) · Answers (PDF) · lesson page
- 1.5 Rounding and estimating: Worksheet (PDF) · Answers (PDF) · lesson page
- 1.6 Roman numerals to 1,000 and years: Worksheet (PDF) · Answers (PDF) · lesson page
- 1.7 Solving number and practical problems: Worksheet (PDF) · Answers (PDF) · lesson page
- Check-up and SATs-style questions: Worksheet (PDF) · Answers (PDF) · lesson page
Exercise P Do you remember?
Non-calculatorKey words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. The value of a digit depends on its column. Find the column, then multiply the digit by the value of the column.
- Write the number in a place-value table. Each column has a name and a value. The coloured digit is the one we want.
Thousands Ones Th H T O 5 2 4 7 - Find which column the digit is in. The digit is 2 and it sits in the hundreds column.1 hundred = 100
- Multiply the digit by the value of the column. There are 2 hundreds.2 × 100 = 200
Check. Say it in words: 2 hundreds is two hundred. ✓
Watch out. The digit is 2 but its value is 200. The same digit is worth different amounts in different columns.
Method. To find 1,000 more, change the thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the thousands digit. 1,000 is one thousand, so we change the thousands digit.
Thousands Ones Th H T O 4 5 7 2 - Add 1 to the thousands digit. 1,000 more means 1 more thousand.4 + 1 = 5 thousands
- Write the new number. The digits that did not change stay the same.4,572 + 1,000 = 5,572
Check. Do the opposite: 5,572 − 1,000 = 4,572. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 3,467 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.3,400 < 3,467 < 3,500
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.3,467 ≈ 3,500 (to the nearest 100)
Check. Distances: 3,467 − 3,400 = 67 and 3,500 − 3,467 = 33. 3,500 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Method. Draw a number line, start at 4 and jump down 7. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 7. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.4 down 7: go down 4 to reach 0, then 3 more below zero → −3
- Write the answer. This is the new temperature.−3°C
Check. Do the opposite: −3 + 7 = 4. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. Split 79 into tens and ones. Write each part in Roman numerals and put them side by side.
- Split the number. Tens first, then ones.79 = 70 + 9
- Write each part. 70 is LXX (50 + 10 + 10). 9 is IX (1 before 10).70 = LXX and 9 = IX
- Put the parts together. Tens on the left.LXX + IX = LXXIX
Check. L + X + X + IX = 50 + 10 + 10 + 9 = 79. ✓
Watch out. Never write the same symbol more than three times in a row.
Reading and writing numbers to 1,000,000
Printable: Worksheet (PDF) · Answers (PDF) · Open this lesson on its own page
In Year 4 you worked with numbers up to 10,000. Now the numbers get much bigger. We will go all the way up to 1,000,000, which is one million! Big numbers are easier to read if the digits are split into groups of three, called periods. We put a comma between the periods. Reading from the right, the first period is Ones (O, T, H), the next is Thousands (Th, TTh, HTh) and the next is Millions (M).
Each column is 10 times bigger than the column on its right. 10 ones make 1 ten, 10 tens make 1 hundred, 10 hundreds make 1 thousand, 10 thousands make 1 ten thousand, and 10 ten thousands make 1 hundred thousand. This chart uses counters to show 306,075. The ten thousands column has no counters, so its digit is a 0, a place holder.
Reading a number in words. Read the digits before the comma as one number and add the word thousand. Then read the last three digits. 306,075 is three hundred and six thousand and seventy-five. We put “and” before the last two digits (the tens and ones). Zeros are not said out loud, but they must be written.
Partitioning. This means splitting a number into the value of each digit: 306,075 = 300,000 + 6,000 + 70 + 5. The value of a digit is the digit times the value of its column. In 306,075, the 3 is worth 300,000 because it is in the hundred thousands column.
| Millions | Thousands | Ones | ||||
|---|---|---|---|---|---|---|
| M | HTh | TTh | Th | H | T | O |
| 1 | 0 | 0 | 0 | 0 | 0 | 0 |
Key words. A digit is one of 0 to 9. A period is a group of three columns. A place holder is a zero that keeps the other digits in the right columns. To partition a number is to split it into the values of its digits.
Key ideas
- The columns, from the right: O, T, H | Th, TTh, HTh | M. Each is 10 times the one on its right.
- Commas split a number into periods of three digits.
- Value of a digit = the digit times the value of its column. The 4 in 340,000 is worth 40,000.
- A zero is a place holder: 405,060 is not the same as 45,060.
- In words, say the thousands period, then “thousand”, then the last three digits. Put “and” before the last two digits.
- 999,999 + 1 = 1,000,000 (one million).
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. The value of a digit depends on its column. Find the column, then multiply the digit by the value of the column.
- Write the number in a place-value table. Each column has a name and a value. The coloured digit is the one we want.
Thousands Ones HTh TTh Th H T O 3 8 4 7 2 9 - Find which column the digit is in. The digit is 8 and it sits in the ten thousands column.1 ten thousand = 10,000
- Multiply the digit by the value of the column. There are 8 ten thousands.8 × 10,000 = 80,000
Check. Say it in words: 8 ten thousands is eighty thousand. ✓
Watch out. The digit is 8 but its value is 80,000. The same digit is worth different amounts in different columns.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Say the number in parts, from left to right: the thousands period first, then the hundreds, then the last two digits.
- Write the number in a place-value table. The comma splits the digits into the Thousands period and the Ones period.
Thousands Ones HTh TTh Th H T O 4 0 8 5 0 7 - Read each part and say it in words. Say the thousands period as a number and then add the word thousand.Thousands period: 408 → four hundred and eight thousand
Hundreds: 5 → five hundred
Last two digits: 7 → seven - Join the parts together. Put “and” before the last two digits (the tens and ones) when there are hundreds or thousands before them.four hundred and eight thousand, five hundred and seven
Check. Read it out loud. It sounds like 408,507. ✓
Watch out. Zeros are never said aloud. 400,060 is “four hundred thousand and sixty”: nothing is said for the empty columns, but they still need a 0 when you write the digits.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Say the number in parts, from left to right: the thousands period first, then the hundreds, then the last two digits.
- Write the number in a place-value table. The comma splits the digits into the Thousands period and the Ones period.
Thousands Ones HTh TTh Th H T O 3 0 0 0 4 0 - Read each part and say it in words. Say the thousands period as a number and then add the word thousand.Thousands period: 300 → three hundred thousand
Last two digits: 40 → forty - Join the parts together. Put “and” before the last two digits (the tens and ones) when there are hundreds or thousands before them.three hundred thousand and forty
Check. Read it out loud. It sounds like 300,040. ✓
Watch out. Zeros are never said aloud. 400,060 is “four hundred thousand and sixty”: nothing is said for the empty columns, but they still need a 0 when you write the digits.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Listen for the words “thousand” and “hundred”. They tell you which period and column each part goes in.
- Split the words into parts. Each part belongs to one period or column.“six hundred and five thousand” → the Thousands period is 605
“two hundred” → 2 in the hundreds column
“nine” → 0 in the tens column and 9 in the ones column - Write the digits in a place-value table. Write a zero in every column that was not mentioned. Each period has three digits (except the first).
Thousands Ones HTh TTh Th H T O 6 0 5 2 0 9 - Write the number. Put a comma between the periods.605,209
Check. Say 605,209 in words: six hundred and five thousand, two hundred and nine. It matches. ✓
Watch out. A zero is a place holder. Without it the digits slip into the wrong columns and the number changes.
Key words. To partition a number is to split it into parts, one part for each digit.
Method. Partition means splitting a number into the value of each of its digits.
- Write the number in a place-value table. This shows how many of each column there are.
Thousands Ones HTh TTh Th H T O 5 3 0 4 0 8 - Work out the value of each digit. Digit times the value of its column.5 hundred thousands = 500,000
3 ten thousands = 30,000
0 thousands = nothing to write
4 hundreds = 400
0 tens = nothing to write
8 ones = 8 - Leave out the zeros. A zero means the column is empty, so there is nothing to add.
- Write the values as an addition. Start with the biggest value.530,408 = 500,000 + 30,000 + 400 + 8
Check. Add them up: 500,000 + 30,000 + 400 + 8 = 530,408. ✓
Watch out. Write 300,000 for 3 hundred thousands, not just 3. Each part keeps its full value.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Count the counters in each column. Each counter is worth the value of its column, so the number of counters is the digit.
- Count the counters in each column. No counters in a column means a zero.HTh column: 2 counters → 2
TTh column: 4 counters → 4
Th column: 7 counters → 7
H column: 0 counters → 0
T column: 3 counters → 3
O column: 6 counters → 6 - Put the digits in a place-value table. Keep the columns in the same order.
Thousands Ones HTh TTh Th H T O 2 4 7 0 3 6 - Read the number. Put a comma between the Thousands period and the Ones period.247,036
Check. Say it in words: two hundred and forty-seven thousand and thirty-six. ✓
Watch out. A column with no counters is a zero. Do not leave it out.
Key words. A place holder is a zero that holds an empty column so the other digits stay in the right place.
Method. Put each part into its own column of a place-value table. Write a zero in any column with nothing in it.
- Read the parts: 3 hundred thousands, 5 ten thousands, 2 hundreds and 8 ones. Each part tells us which column it goes in and how many.
- Put each digit in its column. Start with the biggest column on the left.3 hundred thousands → write 3 in the HTh column
5 ten thousands → write 5 in the TTh column
0 thousands → write 0 in the Th column (nothing here, so write a zero)
2 hundreds → write 2 in the H column
0 tens → write 0 in the T column (nothing here, so write a zero)
8 ones → write 8 in the O column - Read the digits across the table. Put commas between the periods.
Thousands Ones HTh TTh Th H T O 3 5 0 2 0 8
The number is 350,208.
Check. Say it in words: three hundred and fifty thousand, two hundred and eight. It matches the parts. ✓
Watch out. A zero is a place holder. 405,060 and 45,060 are very different numbers.
Method. To find how many hundreds are in a number, read all the digits from the left up to the hundreds column as one number.
- Write the number in a place-value table. Find the hundreds column.
Thousands Ones TTh Th H T O 3 6 4 0 0 - Read the digits up to the H column. Every column on the left is a bigger column. They can all be swapped for hundreds. 1 thousand is 10 hundreds, and so on.The digits 364, read as one number, are 364.
- Write the answer. 364 hundreds
Check. 364 × 100 = 36,400. ✓
Watch out. Do not just read the digit in that column. There are 364 hundreds in 36,400, not 4.
Method. Add 1 to the ones column and carry the 1 all the way along. Then write the answer in digits and words.
- Write the number in a place-value table. Every column is a 9.
Thousands Ones HTh TTh Th H T O 9 9 9 9 9 9 - Add 1 to the ones. 9 + 1 = 10, so write 0 and carry 1. The next column is also 9, so the carry keeps going.9 ones + 1 = 10 ones → 1 ten
9 tens + 1 ten = 10 tens → 1 hundred
… and so on, all the way to the left - Write the new number. Every column is now 0 and there is a new column on the left, the Millions column.
Millions Thousands Ones M HTh TTh Th H T O 1 0 0 0 0 0 0
1,000,000 - Say it in words. 1,000,000 is 1 thousand thousands. We call it one million.one million
Check. 10 × 100,000 = 1,000,000, so there are 10 hundred thousands in one million. ✓
Watch out. 999,999 has six digits. One more has seven. A new column appears when every column is full.
Watch out
Do not forget the place-holder zeros. “Three hundred and five thousand and forty” is 305,040, not 35,040 and not 350,040. Also remember that the value of a digit is not the digit itself: in 460,000 the 6 is worth 60,000.Exercise 1A Reading, writing and partitioning numbers
Non-calculatorKey words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Count the counters in each column. Each counter is worth the value of its column, so the number of counters is the digit.
- Count the counters in each column. No counters in a column means a zero.HTh column: 4 counters → 4
TTh column: 7 counters → 7
Th column: 3 counters → 3
H column: 0 counters → 0
T column: 5 counters → 5
O column: 2 counters → 2 - Put the digits in a place-value table. Keep the columns in the same order.
Thousands Ones HTh TTh Th H T O 4 7 3 0 5 2 - Read the number. Put a comma between the Thousands period and the Ones period.473,052
Check. Say it in words: four hundred and seventy-three thousand and fifty-two. ✓
Watch out. A column with no counters is a zero. Do not leave it out.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Count the counters in each column. Each counter is worth the value of its column, so the number of counters is the digit.
- Count the counters in each column. No counters in a column means a zero.HTh column: 5 counters → 5
TTh column: 0 counters → 0
Th column: 8 counters → 8
H column: 0 counters → 0
T column: 6 counters → 6
O column: 0 counters → 0 - Put the digits in a place-value table. Keep the columns in the same order.
Thousands Ones HTh TTh Th H T O 5 0 8 0 6 0 - Read the number. Put a comma between the Thousands period and the Ones period.508,060
Check. Say it in words: five hundred and eight thousand and sixty. ✓
Watch out. A column with no counters is a zero. Do not leave it out.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. The value of a digit depends on its column. Find the column, then multiply the digit by the value of the column.
- Write the number in a place-value table. Each column has a name and a value. The coloured digit is the one we want.
Thousands Ones HTh TTh Th H T O 6 3 8 2 4 5 - Find which column the digit is in. The digit is 6 and it sits in the hundred thousands column.1 hundred thousand = 100,000
- Multiply the digit by the value of the column. There are 6 hundred thousands.6 × 100,000 = 600,000
Check. Say it in words: 6 hundred thousands is six hundred thousand. ✓
Watch out. The digit is 6 but its value is 600,000. The same digit is worth different amounts in different columns.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. The value of a digit depends on its column. Find the column, then multiply the digit by the value of the column.
- Write the number in a place-value table. Each column has a name and a value. The coloured digit is the one we want.
Thousands Ones TTh Th H T O 9 2 8 1 6 - Find which column the digit is in. The digit is 9 and it sits in the ten thousands column.1 ten thousand = 10,000
- Multiply the digit by the value of the column. There are 9 ten thousands.9 × 10,000 = 90,000
Check. Say it in words: 9 ten thousands is ninety thousand. ✓
Watch out. The digit is 9 but its value is 90,000. The same digit is worth different amounts in different columns.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. The value of a digit depends on its column. Find the column, then multiply the digit by the value of the column.
- Write the number in a place-value table. Each column has a name and a value. The coloured digit is the one we want.
Thousands Ones HTh TTh Th H T O 4 0 7 1 5 3 - Find which column the digit is in. The digit is 7 and it sits in the thousands column.1 thousand = 1,000
- Multiply the digit by the value of the column. There are 7 thousands.7 × 1,000 = 7,000
Check. Say it in words: 7 thousands is seven thousand. ✓
Watch out. The digit is 7 but its value is 7,000. The same digit is worth different amounts in different columns.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. The value of a digit depends on its column. Find the column, then multiply the digit by the value of the column.
- Write the number in a place-value table. Each column has a name and a value. The coloured digit is the one we want.
Thousands Ones HTh TTh Th H T O 5 2 0 8 9 4 - Find which column the digit is in. The digit is 9 and it sits in the tens column.1 ten = 10
- Multiply the digit by the value of the column. There are 9 tens.9 × 10 = 90
Check. Say it in words: 9 tens is ninety. ✓
Watch out. The digit is 9 but its value is 90. The same digit is worth different amounts in different columns.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Say the number in parts, from left to right: the thousands period first, then the hundreds, then the last two digits.
- Write the number in a place-value table. The comma splits the digits into the Thousands period and the Ones period.
Thousands Ones TTh Th H T O 3 8 2 0 5 - Read each part and say it in words. Say the thousands period as a number and then add the word thousand.Thousands period: 38 → thirty-eight thousand
Hundreds: 2 → two hundred
Last two digits: 5 → five - Join the parts together. Put “and” before the last two digits (the tens and ones) when there are hundreds or thousands before them.thirty-eight thousand, two hundred and five
Check. Read it out loud. It sounds like 38,205. ✓
Watch out. Zeros are never said aloud. 400,060 is “four hundred thousand and sixty”: nothing is said for the empty columns, but they still need a 0 when you write the digits.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Say the number in parts, from left to right: the thousands period first, then the hundreds, then the last two digits.
- Write the number in a place-value table. The comma splits the digits into the Thousands period and the Ones period.
Thousands Ones HTh TTh Th H T O 2 7 0 0 4 0 - Read each part and say it in words. Say the thousands period as a number and then add the word thousand.Thousands period: 270 → two hundred and seventy thousand
Last two digits: 40 → forty - Join the parts together. Put “and” before the last two digits (the tens and ones) when there are hundreds or thousands before them.two hundred and seventy thousand and forty
Check. Read it out loud. It sounds like 270,040. ✓
Watch out. Zeros are never said aloud. 400,060 is “four hundred thousand and sixty”: nothing is said for the empty columns, but they still need a 0 when you write the digits.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Say the number in parts, from left to right: the thousands period first, then the hundreds, then the last two digits.
- Write the number in a place-value table. The comma splits the digits into the Thousands period and the Ones period.
Thousands Ones HTh TTh Th H T O 6 0 4 3 0 0 - Read each part and say it in words. Say the thousands period as a number and then add the word thousand.Thousands period: 604 → six hundred and four thousand
Hundreds: 3 → three hundred - Join the parts together. Put “and” before the last two digits (the tens and ones) when there are hundreds or thousands before them.six hundred and four thousand, three hundred
Check. Read it out loud. It sounds like 604,300. ✓
Watch out. Zeros are never said aloud. 400,060 is “four hundred thousand and sixty”: nothing is said for the empty columns, but they still need a 0 when you write the digits.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Say the number in parts, from left to right: the thousands period first, then the hundreds, then the last two digits.
- Write the number in a place-value table. The comma splits the digits into the Thousands period and the Ones period.
Thousands Ones HTh TTh Th H T O 9 0 0 0 0 9 - Read each part and say it in words. Say the thousands period as a number and then add the word thousand.Thousands period: 900 → nine hundred thousand
Last two digits: 9 → nine - Join the parts together. Put “and” before the last two digits (the tens and ones) when there are hundreds or thousands before them.nine hundred thousand and nine
Check. Read it out loud. It sounds like 900,009. ✓
Watch out. Zeros are never said aloud. 400,060 is “four hundred thousand and sixty”: nothing is said for the empty columns, but they still need a 0 when you write the digits.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Listen for the words “thousand” and “hundred”. They tell you which period and column each part goes in.
- Split the words into parts. Each part belongs to one period or column.“fifty-two thousand” → the Thousands period is 52
“six hundred” → 6 in the hundreds column
“eight” → 0 in the tens column and 8 in the ones column - Write the digits in a place-value table. Write a zero in every column that was not mentioned. Each period has three digits (except the first).
Thousands Ones TTh Th H T O 5 2 6 0 8 - Write the number. Put a comma between the periods.52,608
Check. Say 52,608 in words: fifty-two thousand, six hundred and eight. It matches. ✓
Watch out. A zero is a place holder. Without it the digits slip into the wrong columns and the number changes.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Listen for the words “thousand” and “hundred”. They tell you which period and column each part goes in.
- Split the words into parts. Each part belongs to one period or column.“three hundred and forty thousand” → the Thousands period is 340
no hundreds are said → 0 in the hundreds column
“seven” → 0 in the tens column and 7 in the ones column - Write the digits in a place-value table. Write a zero in every column that was not mentioned. Each period has three digits (except the first).
Thousands Ones HTh TTh Th H T O 3 4 0 0 0 7 - Write the number. Put a comma between the periods.340,007
Check. Say 340,007 in words: three hundred and forty thousand and seven. It matches. ✓
Watch out. A zero is a place holder. Without it the digits slip into the wrong columns and the number changes.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Listen for the words “thousand” and “hundred”. They tell you which period and column each part goes in.
- Split the words into parts. Each part belongs to one period or column.“six hundred and six thousand” → the Thousands period is 606
“six hundred” → 6 in the hundreds column
“six” → 0 in the tens column and 6 in the ones column - Write the digits in a place-value table. Write a zero in every column that was not mentioned. Each period has three digits (except the first).
Thousands Ones HTh TTh Th H T O 6 0 6 6 0 6 - Write the number. Put a comma between the periods.606,606
Check. Say 606,606 in words: six hundred and six thousand, six hundred and six. It matches. ✓
Watch out. A zero is a place holder. Without it the digits slip into the wrong columns and the number changes.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Listen for the words “thousand” and “hundred”. They tell you which period and column each part goes in.
- Split the words into parts. Each part belongs to one period or column.“nine hundred thousand” → the Thousands period is 900
no hundreds are said → 0 in the hundreds column
“ninety” → 9 in the tens column and 0 in the ones column - Write the digits in a place-value table. Write a zero in every column that was not mentioned. Each period has three digits (except the first).
Thousands Ones HTh TTh Th H T O 9 0 0 0 9 0 - Write the number. Put a comma between the periods.900,090
Check. Say 900,090 in words: nine hundred thousand and ninety. It matches. ✓
Watch out. A zero is a place holder. Without it the digits slip into the wrong columns and the number changes.
Key words. To partition a number is to split it into parts, one part for each digit.
Method. Partition means splitting a number into the value of each of its digits.
- Write the number in a place-value table. This shows how many of each column there are.
Thousands Ones HTh TTh Th H T O 4 8 2 6 1 5 - Work out the value of each digit. Digit times the value of its column.4 hundred thousands = 400,000
8 ten thousands = 80,000
2 thousands = 2,000
6 hundreds = 600
1 ten = 10
5 ones = 5 - Write the values as an addition. Start with the biggest value.482,615 = 400,000 + 80,000 + 2,000 + 600 + 10 + 5
Check. Add them up: 400,000 + 80,000 + 2,000 + 600 + 10 + 5 = 482,615. ✓
Watch out. Write 300,000 for 3 hundred thousands, not just 3. Each part keeps its full value.
Key words. To partition a number is to split it into parts, one part for each digit.
Method. Partition means splitting a number into the value of each of its digits.
- Write the number in a place-value table. This shows how many of each column there are.
Thousands Ones HTh TTh Th H T O 7 0 3 0 4 0 - Work out the value of each digit. Digit times the value of its column.7 hundred thousands = 700,000
0 ten thousands = nothing to write
3 thousands = 3,000
0 hundreds = nothing to write
4 tens = 40
0 ones = nothing to write - Leave out the zeros. A zero means the column is empty, so there is nothing to add.
- Write the values as an addition. Start with the biggest value.703,040 = 700,000 + 3,000 + 40
Check. Add them up: 700,000 + 3,000 + 40 = 703,040. ✓
Watch out. Write 300,000 for 3 hundred thousands, not just 3. Each part keeps its full value.
Key words. To partition a number is to split it into parts, one part for each digit.
Method. Partition means splitting a number into the value of each of its digits.
- Write the number in a place-value table. This shows how many of each column there are.
Thousands Ones HTh TTh Th H T O 2 5 0 0 0 8 - Work out the value of each digit. Digit times the value of its column.2 hundred thousands = 200,000
5 ten thousands = 50,000
0 thousands = nothing to write
0 hundreds = nothing to write
0 tens = nothing to write
8 ones = 8 - Leave out the zeros. A zero means the column is empty, so there is nothing to add.
- Write the values as an addition. Start with the biggest value.250,008 = 200,000 + 50,000 + 8
Check. Add them up: 200,000 + 50,000 + 8 = 250,008. ✓
Watch out. Write 300,000 for 3 hundred thousands, not just 3. Each part keeps its full value.
Key words. To partition a number is to split it into parts, one part for each digit.
Method. Partition means splitting a number into the value of each of its digits.
- Write the number in a place-value table. This shows how many of each column there are.
Thousands Ones TTh Th H T O 9 6 0 7 0 - Work out the value of each digit. Digit times the value of its column.9 ten thousands = 90,000
6 thousands = 6,000
0 hundreds = nothing to write
7 tens = 70
0 ones = nothing to write - Leave out the zeros. A zero means the column is empty, so there is nothing to add.
- Write the values as an addition. Start with the biggest value.96,070 = 90,000 + 6,000 + 70
Check. Add them up: 90,000 + 6,000 + 70 = 96,070. ✓
Watch out. Write 300,000 for 3 hundred thousands, not just 3. Each part keeps its full value.
Key words. A place holder is a zero that holds an empty column so the other digits stay in the right place.
Method. Put each part into its own column of a place-value table. Write a zero in any column with nothing in it.
- Read the parts: 6 hundred thousands, 4 thousands and 9 tens. Each part tells us which column it goes in and how many.
- Put each digit in its column. Start with the biggest column on the left.6 hundred thousands → write 6 in the HTh column
0 ten thousands → write 0 in the TTh column (nothing here, so write a zero)
4 thousands → write 4 in the Th column
0 hundreds → write 0 in the H column (nothing here, so write a zero)
9 tens → write 9 in the T column
0 ones → write 0 in the O column (nothing here, so write a zero) - Read the digits across the table. Put commas between the periods.
Thousands Ones HTh TTh Th H T O 6 0 4 0 9 0
The number is 604,090.
Check. Say it in words: six hundred and four thousand and ninety. It matches the parts. ✓
Watch out. A zero is a place holder. 405,060 and 45,060 are very different numbers.
Key words. A place holder is a zero that holds an empty column so the other digits stay in the right place.
Method. Put each part into its own column of a place-value table. Write a zero in any column with nothing in it.
- Read the parts: 3 hundred thousands, 7 ten thousands and 2 hundreds. Each part tells us which column it goes in and how many.
- Put each digit in its column. Start with the biggest column on the left.3 hundred thousands → write 3 in the HTh column
7 ten thousands → write 7 in the TTh column
0 thousands → write 0 in the Th column (nothing here, so write a zero)
2 hundreds → write 2 in the H column
0 tens → write 0 in the T column (nothing here, so write a zero)
0 ones → write 0 in the O column (nothing here, so write a zero) - Read the digits across the table. Put commas between the periods.
Thousands Ones HTh TTh Th H T O 3 7 0 2 0 0
The number is 370,200.
Check. Say it in words: three hundred and seventy thousand, two hundred. It matches the parts. ✓
Watch out. A zero is a place holder. 405,060 and 45,060 are very different numbers.
Key words. A place holder is a zero that holds an empty column so the other digits stay in the right place.
Method. Put each part into its own column of a place-value table. Write a zero in any column with nothing in it.
- Read the parts: 800,000 + 5,000 + 40 + 3. Each part tells us which column it goes in and how many.
- Put each digit in its column. Start with the biggest column on the left.8 hundred thousands → write 8 in the HTh column
0 ten thousands → write 0 in the TTh column (nothing here, so write a zero)
5 thousands → write 5 in the Th column
0 hundreds → write 0 in the H column (nothing here, so write a zero)
4 tens → write 4 in the T column
3 ones → write 3 in the O column - Read the digits across the table. Put commas between the periods.
Thousands Ones HTh TTh Th H T O 8 0 5 0 4 3
The number is 805,043.
Check. Say it in words: eight hundred and five thousand and forty-three. It matches the parts. ✓
Watch out. A zero is a place holder. 405,060 and 45,060 are very different numbers.
Key words. A place holder is a zero that holds an empty column so the other digits stay in the right place.
Method. Put each part into its own column of a place-value table. Write a zero in any column with nothing in it.
- Read the parts: 200,000 + 90,000 + 6. Each part tells us which column it goes in and how many.
- Put each digit in its column. Start with the biggest column on the left.2 hundred thousands → write 2 in the HTh column
9 ten thousands → write 9 in the TTh column
0 thousands → write 0 in the Th column (nothing here, so write a zero)
0 hundreds → write 0 in the H column (nothing here, so write a zero)
0 tens → write 0 in the T column (nothing here, so write a zero)
6 ones → write 6 in the O column - Read the digits across the table. Put commas between the periods.
Thousands Ones HTh TTh Th H T O 2 9 0 0 0 6
The number is 290,006.
Check. Say it in words: two hundred and ninety thousand and six. It matches the parts. ✓
Watch out. A zero is a place holder. 405,060 and 45,060 are very different numbers.
Method. Find the ten thousands digit in each number. It is the second digit from the left in a six-digit number.
- Write each number in a place-value table. This shows which column each digit is in.
Thousands Ones HTh TTh Th H T O 7 1 0 4 5 8 Thousands Ones HTh TTh Th H T O 1 0 7 4 5 8 Thousands Ones HTh TTh Th H T O 1 7 0 4 5 8 Thousands Ones HTh TTh Th H T O 1 0 0 7 4 5 - Look at the coloured ten thousands digit in each. We want the one that is a 7.710,458: ten thousands digit is 1
107,458: ten thousands digit is 0
170,458: ten thousands digit is 7
100,745: ten thousands digit is 0 - Choose the number. C (170,458)
Check. 170,458 = 100,000 + 70,000 + 400 + 50 + 8. The 7 is worth 70,000. ✓
Watch out. 710,458 has a 7 too, but it is in the hundred thousands column.
Method. To find how many thousands are in a number, read all the digits from the left up to the thousands column as one number.
- Write the number in a place-value table. Find the thousands column.
Thousands Ones TTh Th H T O 7 2 0 0 0 - Read the digits up to the Th column. Every column on the left is a bigger column. They can all be swapped for thousands. 1 ten thousand is 10 thousands, and so on.The digits 72, read as one number, are 72.
- Write the answer. 72 thousands
Check. 72 × 1,000 = 72,000. ✓
Watch out. Do not just read the digit in that column. There are 72 thousands in 72,000, not 2.
Method. To find how many hundreds are in a number, read all the digits from the left up to the hundreds column as one number.
- Write the number in a place-value table. Find the hundreds column.
Thousands Ones TTh Th H T O 4 5 3 0 0 - Read the digits up to the H column. Every column on the left is a bigger column. They can all be swapped for hundreds. 1 thousand is 10 hundreds, and so on.The digits 453, read as one number, are 453.
- Write the answer. 453 hundreds
Check. 453 × 100 = 45,300. ✓
Watch out. Do not just read the digit in that column. There are 453 hundreds in 45,300, not 3.
Method. To find how many tens are in a number, read all the digits from the left up to the tens column as one number.
- Write the number in a place-value table. Find the tens column.
Thousands Ones Th H T O 8 7 4 0 - Read the digits up to the T column. Every column on the left is a bigger column. They can all be swapped for tens. 1 hundred is 10 tens, and so on.The digits 874, read as one number, are 874.
- Write the answer. 874 tens
Check. 874 × 10 = 8,740. ✓
Watch out. Do not just read the digit in that column. There are 874 tens in 8,740, not 4.
Method. To find how many hundreds are in a number, read all the digits from the left up to the hundreds column as one number.
- Write the number in a place-value table. Find the hundreds column.
Thousands Ones HTh TTh Th H T O 1 0 0 0 0 0 - Read the digits up to the H column. Every column on the left is a bigger column. They can all be swapped for hundreds. 1 thousand is 10 hundreds, and so on.The digits 1000, read as one number, are 1,000.
- Write the answer. 1,000 hundreds
Check. 1,000 × 100 = 100,000. ✓
Watch out. Do not just read the digit in that column. There are 1,000 hundreds in 100,000, not 0.
Key words. A place holder is a zero that holds an empty column so the other digits stay in the right place.
Method. Put each part into its own column of a place-value table. Write a zero in any column with nothing in it.
- Read the parts: 4 boxes of 100,000 + 2 boxes of 10,000 + 6 boxes of 1,000 + 5 loose coins. Each part tells us which column it goes in and how many.
- Put each digit in its column. Start with the biggest column on the left.4 hundred thousands → write 4 in the HTh column
2 ten thousands → write 2 in the TTh column
6 thousands → write 6 in the Th column
0 hundreds → write 0 in the H column (nothing here, so write a zero)
0 tens → write 0 in the T column (nothing here, so write a zero)
5 ones → write 5 in the O column - Read the digits across the table. Put commas between the periods.
Thousands Ones HTh TTh Th H T O 4 2 6 0 0 5
The number is 426,005.
Check. Say it in words: four hundred and twenty-six thousand and five. It matches the parts. ✓
Watch out. A zero is a place holder. 405,060 and 45,060 are very different numbers.
Method. A six-digit number cannot start with 0. The smallest digit for the hundred thousands column is 1, and every other column is 0.
- Choose the first digit. It cannot be 0, so the smallest choice is 1.HTh = 1
- Make every other column as small as possible. 0 is the smallest digit.TTh = 0, Th = 0, H = 0, T = 0, O = 0
- Write the number. 100,000
Check. 99,999 has only five digits, and 100,000 is one more than 99,999. ✓
Method. Use the biggest digit, 9, in every column.
- Choose the biggest digit for each column. 9 is the biggest digit.HTh = 9, TTh = 9, Th = 9, H = 9, T = 9, O = 9
- Write the number. 999,999
Check. One more makes a seven-digit number: 1,000,000. ✓
Method. Add 1 to the ones column and carry the 1 all the way along. Then write the answer in digits and words.
- Write the number in a place-value table. Every column is a 9.
Thousands Ones HTh TTh Th H T O 9 9 9 9 9 9 - Add 1 to the ones. 9 + 1 = 10, so write 0 and carry 1. The next column is also 9, so the carry keeps going.9 ones + 1 = 10 ones → 1 ten
9 tens + 1 ten = 10 tens → 1 hundred
… and so on, all the way to the left - Write the new number. Every column is now 0 and there is a new column on the left, the Millions column.
Millions Thousands Ones M HTh TTh Th H T O 1 0 0 0 0 0 0
1,000,000 - Say it in words. 1,000,000 is 1 thousand thousands. We call it one million.one million
Check. 10 × 100,000 = 1,000,000, so there are 10 hundred thousands in one million. ✓
Watch out. 999,999 has six digits. One more has seven. A new column appears when every column is full.
Method. Say the words in parts and write each part in the right column. Then compare with Noah’s number.
- Say the words in parts. “Three hundred and five thousand” is the thousands period: 305. “And forty” is the last two digits: 4 tens and 0 ones. No hundreds are said.305 | 0 hundreds, 4 tens, 0 ones
- Write it in a place-value table. The empty hundreds column and the ones column need zeros.
Thousands Ones HTh TTh Th H T O 3 0 5 0 4 0 - Compare with Noah’s number. Noah wrote 350,040. That has 5 ten thousands and 0 thousands, but the words say 0 ten thousands and 5 thousands.350,040 is three hundred and fifty thousand and forty.
He swapped the 0 and the 5.
Check. Say 305,040 in words: three hundred and five thousand and forty. ✓
Watch out. Each word group tells you exactly which columns to fill. Write the thousands period first.
Method. Write each one as a six-digit number, then find the one that is different.
- Write each as a number. Use place value.400,050
400,000 + 50 = 400,050
4 hundred thousands and 5 tens = 400,000 + 50 = 400,050
450,000 - Compare them. Three are 400,050 but one is 450,000.400,050, 400,050, 400,050, 450,000
- Write the odd one out. 450,000
Check. 450,000 has 5 ten thousands. The others have 5 tens. ✓
Watch out. Look at which column the 5 is in.
“The value of a digit is bigger than the digit itself.”
Method. Try some digits in different columns. If it works for some and not others, the answer is “sometimes”.
- Try the 3 in 300,000. The 3 is in the hundred thousands column.Value = 300,000. That is bigger than 3. It works here.
- Try the 7 in 5,347. The 7 is in the ones column.Value = 7. That is the same as the digit, not bigger. It does not work here.
- Try a zero. A 0 in any column is worth nothing.Value = 0. Not bigger than 0.
- Write the answer. It works for some digits and not for others.Sometimes
Check. It is bigger for digits 1 to 9 that are not in the ones column. ✓
Watch out. One example that works does not prove “always”. Look for one that breaks the rule.
Method. Work out 10 lots of 100,000 and compare with one million.
- Count in hundred thousands. Add 100,000 each time.1 × 100,000 = 100,000
2 × 100,000 = 200,000
3 × 100,000 = 300,000
4 × 100,000 = 400,000
5 × 100,000 = 500,000
6 × 100,000 = 600,000
7 × 100,000 = 700,000
8 × 100,000 = 800,000
9 × 100,000 = 900,000
10 × 100,000 = 1,000,000 - Find the tenth number. 10 hundred thousands is the last line.10 × 100,000 = 1,000,000
- Answer Amira. Yes. There are 10 hundred thousands in one million.
Check. Using the chart: the Millions column is 10 times the HTh column. ✓
Watch out. Each column is 10 times the column on its right. That is why a new column starts after ten of the last one.
My hundred thousands digit is twice my ten thousands digit.
My thousands digit is 0.
My hundreds digit is the same as my ten thousands digit.
My tens digit is 5 more than my ones digit.
My digits add up to 21.
My ones digit is not 0 and I am more than 500,000.
What number am I?
Method. Use the easy clues first to write the shape of the number. Then use the digit total to find the possible numbers.
- Write what we know. Let the ten thousands digit be k. Then the hundred thousands digit is 2k, the thousands digit is 0 and the hundreds digit is k. The tens digit is 5 more than the ones digit.2k | k | 0 | k | (ones + 5) | ones
- Use the digit total. The digits add up to 21, so 2k + k + 0 + k + (ones + 5) + ones = 21.4k + 2 × ones + 5 = 21
4k + 2 × ones = 16 - Try each possible k. k can be 1, 2, 3 or 4 (2k must be one digit). Work out the ones digit each time. (k = 1 fails: the ones digit would be 6 and the tens digit 11, which is too big.)k = 2: ones = 4, tens = 9, number = 420,294
k = 3: ones = 2, tens = 7, number = 630,372
k = 4: ones = 0, tens = 5, number = 840,450 - Use the last clue. The ones digit is not 0, and the number is more than 500,000.420,294 is less than 500,000, so no. 840,450 has ones digit 0, so no.
Only 630,372 is left.
Check. 630,372: 6 = 2 × 3 ✓, thousands 0 ✓, hundreds 3 ✓, tens 7 = 2 + 5 ✓, 6+3+0+3+7+2 = 21 ✓, ones not 0 ✓, more than 500,000 ✓.
Watch out. Check your answer against every clue.
Comparing and ordering numbers to 1,000,000
Printable: Worksheet (PDF) · Answers (PDF) · Open this lesson on its own page
Comparing. To decide which number is bigger, first look at how many digits each number has. A number with more digits is bigger (as long as it does not start with 0). If both have the same number of digits, line the digits up in a place-value table and compare from the left. The first column that is different decides.
| Thousands | Ones | |||||
|---|---|---|---|---|---|---|
| HTh | TTh | Th | H | T | O | |
| 482,619 | 4 | 8 | 2 | 6 | 1 | 9 |
| 482,691 | 4 | 8 | 2 | 6 | 9 | 1 |
We use three signs: < means “is less than”, > means “is greater than” and = means “is equal to”. The open end of the sign faces the bigger number. To order numbers, compare them in pairs. Ascending order is smallest first. Descending order is biggest first.
Number lines. To read a number line, work out what one gap is worth: take the difference between two labelled numbers and divide by the number of gaps. This line goes from 0 to 1,000,000 in 10 gaps, so each gap is 1,000,000 ÷ 10 = 100,000. The arrow is between 600,000 and 700,000. If the arrow is not exactly on a mark we estimate a number close to it. Halfway between 600,000 and 700,000 is 650,000.
Making numbers with digit cards. To make the largest number, put the biggest digit in the biggest column, then the next biggest, and so on. To make the smallest number, put the smallest digit first, but never put 0 in the first column. A six-digit number cannot start with 0.
Key words. Ascending means getting bigger. Descending means getting smaller. To estimate is to give a sensible answer that is close to the exact one.
Key ideas
- More digits means a bigger number (if no number starts with 0).
- Same number of digits: compare from the left. The first column that is different decides.
- < less than, > greater than, = equal to. The open end faces the bigger number.
- On a number line, work out what one gap is worth before you read the arrow.
- Largest number: biggest digit first. Smallest number: smallest digit first, but not 0.
- Halfway between two numbers: add them and halve the total.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones HTh TTh Th H T O 356,742 3 5 6 7 4 2 356,724 3 5 6 7 2 4 - Compare the digits from the left. The first column where they are different decides which number is bigger.hundred thousands: 3 and 3 are the same, so look at the next column.
ten thousands: 5 and 5 are the same, so look at the next column.
thousands: 6 and 6 are the same, so look at the next column.
hundreds: 7 and 7 are the same, so look at the next column.
tens: 4 and 2 are different. 4 > 2, so 356,742 is bigger. - Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.356,742 > 356,724
Check. Picture a number line: 356,724 is to the left of 356,742. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones HTh TTh Th H T O 98,765 9 8 7 6 5 100,234 1 0 0 2 3 4 - Count the digits. A number with more digits is bigger (when no number starts with 0).100,234 has 6 digits and 98,765 has 5 digits, so 100,234 is bigger.
- Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.98,765 < 100,234
Check. Picture a number line: 98,765 is to the left of 100,234. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write each side as one number. We can only compare numbers when they are written the usual way.300,000 + 4,000 = 304,000
340,000 = 340,000 - Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones HTh TTh Th H T O 304,000 3 0 4 0 0 0 340,000 3 4 0 0 0 0 - Compare the digits from the left. The first column where they are different decides which number is bigger.hundred thousands: 3 and 3 are the same, so look at the next column.
ten thousands: 0 and 4 are different. 0 < 4, so 304,000 is smaller. - Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.304,000 < 340,000
Check. Picture a number line: 304,000 is to the left of 340,000. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Smallest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 345,678 3 4 5 6 7 8 345,768 3 4 5 7 6 8 354,678 3 5 4 6 7 8 345,687 3 4 5 6 8 7 34,568 3 4 5 6 8 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.34,568 and 345,678: 345,678 has 6 digits and 34,568 has 5 digits, so 345,678 is bigger.
345,678 and 345,687: tens: 7 and 8 are different. 7 < 8, so 345,678 is smaller.
345,687 and 345,768: hundreds: 6 and 7 are different. 6 < 7, so 345,687 is smaller.
345,768 and 354,678: ten thousands: 4 and 5 are different. 4 < 5, so 345,768 is smaller. - Write them smallest first. Check you have used every number once.34,568, 345,678, 345,687, 345,768, 354,678
Check. Count the numbers: 5 in the question and 5 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Biggest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 807,060 8 0 7 0 6 0 870,600 8 7 0 6 0 0 806,070 8 0 6 0 7 0 87,060 8 7 0 6 0 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.87,060 and 806,070: 806,070 has 6 digits and 87,060 has 5 digits, so 806,070 is bigger.
806,070 and 807,060: thousands: 6 and 7 are different. 6 < 7, so 806,070 is smaller.
807,060 and 870,600: ten thousands: 0 and 7 are different. 0 < 7, so 807,060 is smaller. - Write them biggest first. Check you have used every number once.870,600, 807,060, 806,070, 87,060
Check. Count the numbers: 4 in the question and 4 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Method. Find out what each small mark is worth, then count on from a number you can read.
- Count the gaps between two labelled numbers. The line goes from 300,000 to 400,000 in 10 equal gaps.400,000 − 300,000 = 100,000
- Work out what one gap is worth. Share the distance equally between the gaps.100,000 ÷ 10 = 10,000
- Count on from the start to the arrow. The arrow is 6 gaps after 300,000.300,000 + 6 × 10,000 = 300,000 + 60,000 = 360,000
Check. Count back from 400,000: 4 gaps back is 400,000 − 40,000 = 360,000. ✓
Watch out. Do not read the nearest label. Count the small marks to find the exact number.
Method. Work out what each gap is worth. Then decide which two gaps the arrow is between and how far along it is.
- Work out what one gap is worth. The line goes from 0 to 1,000,000 in 10 equal gaps.1,000,000 ÷ 10 = 100,000
- Find the two numbers either side of the arrow. The arrow is after 6 gaps, but before 7 gaps.600,000 < arrow < 700,000
- Decide how far along the arrow is. Halfway between 600,000 and 700,000 is 650,000.The arrow is close to 650,000.
- Choose the best estimate. Pick the option nearest to the arrow.C (650,000)
Check. The other options are far away: 150,000, 450,000, 950,000. ✓
Watch out. An estimate is a sensible guess. You do not need the exact number.
Method. Make the largest by putting the cards in order, biggest first. Make the smallest by putting them in order, smallest first (with a non-zero digit in front).
- Largest: put the digits in order, biggest first. The biggest digit in the biggest column gives the biggest number.9, 7, 5, 4, 2, 0 → 975,420
- Smallest: put the digits in order, smallest first. That would start with 0, but a six-digit number cannot start with 0.0, 2, 4, 5, 7, 9
- Swap the first two digits. The smallest digit that is not 0 goes first, then the 0.2, 0, 4, 5, 7, 9 → 204,579
Check. Check the smallest has six digits and uses all the cards once. 204,579 does. ✓
Watch out. A leading zero is not allowed: 024,579 is really a five-digit number.
Method. The number halfway between two numbers is the same distance from both. Find the gap between them, halve it, then add that to the smaller number.
- Find the gap between the two numbers. Subtract the smaller from the bigger.360,000 − 340,000 = 20,000
- Halve the gap. Halfway is half of the gap away from each number.20,000 ÷ 2 = 10,000
- Add half the gap to the smaller number. This moves us to the middle.340,000 + 10,000 = 350,000
Check. Another way: add the numbers and halve. 340,000 + 360,000 = 700,000 and 700,000 ÷ 2 = 350,000. ✓
Watch out. Halfway is not the average of the digits. Use the whole numbers.
Watch out
Start on the left when you compare, not the right. 98,765 is smaller than 100,234 even though 9 is bigger than 1, because 98,765 has only five digits and 100,234 has six. And a zero cannot go first: the smallest six-digit number is 100,000, not 000,000.Exercise 1B Comparing and ordering
Non-calculatorKey words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones HTh TTh Th H T O 356,742 3 5 6 7 4 2 356,724 3 5 6 7 2 4 - Compare the digits from the left. The first column where they are different decides which number is bigger.hundred thousands: 3 and 3 are the same, so look at the next column.
ten thousands: 5 and 5 are the same, so look at the next column.
thousands: 6 and 6 are the same, so look at the next column.
hundreds: 7 and 7 are the same, so look at the next column.
tens: 4 and 2 are different. 4 > 2, so 356,742 is bigger. - Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.356,742 > 356,724
Check. Picture a number line: 356,724 is to the left of 356,742. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones HTh TTh Th H T O 89,999 8 9 9 9 9 100,001 1 0 0 0 0 1 - Count the digits. A number with more digits is bigger (when no number starts with 0).100,001 has 6 digits and 89,999 has 5 digits, so 100,001 is bigger.
- Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.89,999 < 100,001
Check. Picture a number line: 89,999 is to the left of 100,001. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write each side as one number. We can only compare numbers when they are written the usual way.400,000 + 5,000 = 405,000
450,000 = 450,000 - Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones HTh TTh Th H T O 405,000 4 0 5 0 0 0 450,000 4 5 0 0 0 0 - Compare the digits from the left. The first column where they are different decides which number is bigger.hundred thousands: 4 and 4 are the same, so look at the next column.
ten thousands: 0 and 5 are different. 0 < 5, so 405,000 is smaller. - Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.405,000 < 450,000
Check. Picture a number line: 405,000 is to the left of 450,000. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones HTh TTh Th H T O 620,300 6 2 0 3 0 0 62,030 6 2 0 3 0 - Count the digits. A number with more digits is bigger (when no number starts with 0).620,300 has 6 digits and 62,030 has 5 digits, so 620,300 is bigger.
- Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.620,300 > 62,030
Check. Picture a number line: 62,030 is to the left of 620,300. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write each side as one number. We can only compare numbers when they are written the usual way.seven hundred thousand = 700,000
700,000 = 700,000 - Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones HTh TTh Th H T O 700,000 7 0 0 0 0 0 700,000 7 0 0 0 0 0 - Compare the digits from the left. The first column where they are different decides which number is bigger.Every column is the same.
- Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.700,000 = 700,000
Check. Both are 700,000. ✓
Watch out. Equal numbers can be written in different ways, so write both as digits first.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Millions Thousands Ones M HTh TTh Th H T O 999,999 9 9 9 9 9 9 1,000,000 1 0 0 0 0 0 0 - Count the digits. A number with more digits is bigger (when no number starts with 0).1,000,000 has 7 digits and 999,999 has 6 digits, so 1,000,000 is bigger.
- Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.999,999 < 1,000,000
Check. Picture a number line: 999,999 is to the left of 1,000,000. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Smallest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 534,210 5 3 4 2 1 0 534,120 5 3 4 1 2 0 543,210 5 4 3 2 1 0 53,421 5 3 4 2 1 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.53,421 and 534,120: 534,120 has 6 digits and 53,421 has 5 digits, so 534,120 is bigger.
534,120 and 534,210: hundreds: 1 and 2 are different. 1 < 2, so 534,120 is smaller.
534,210 and 543,210: ten thousands: 3 and 4 are different. 3 < 4, so 534,210 is smaller. - Write them smallest first. Check you have used every number once.53,421, 534,120, 534,210, 543,210
Check. Count the numbers: 4 in the question and 4 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Smallest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 706,040 7 0 6 0 4 0 760,040 7 6 0 0 4 0 706,400 7 0 6 4 0 0 76,040 7 6 0 4 0 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.76,040 and 706,040: 706,040 has 6 digits and 76,040 has 5 digits, so 706,040 is bigger.
706,040 and 706,400: hundreds: 0 and 4 are different. 0 < 4, so 706,040 is smaller.
706,400 and 760,040: ten thousands: 0 and 6 are different. 0 < 6, so 706,400 is smaller. - Write them smallest first. Check you have used every number once.76,040, 706,040, 706,400, 760,040
Check. Count the numbers: 4 in the question and 4 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Smallest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 999,001 9 9 9 0 0 1 990,901 9 9 0 9 0 1 909,901 9 0 9 9 0 1 999,010 9 9 9 0 1 0 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.909,901 and 990,901: ten thousands: 0 and 9 are different. 0 < 9, so 909,901 is smaller.
990,901 and 999,001: thousands: 0 and 9 are different. 0 < 9, so 990,901 is smaller.
999,001 and 999,010: tens: 0 and 1 are different. 0 < 1, so 999,001 is smaller. - Write them smallest first. Check you have used every number once.909,901, 990,901, 999,001, 999,010
Check. Count the numbers: 4 in the question and 4 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Biggest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 250,639 2 5 0 6 3 9 205,639 2 0 5 6 3 9 250,369 2 5 0 3 6 9 25,639 2 5 6 3 9 205,936 2 0 5 9 3 6 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.25,639 and 205,639: 205,639 has 6 digits and 25,639 has 5 digits, so 205,639 is bigger.
205,639 and 205,936: hundreds: 6 and 9 are different. 6 < 9, so 205,639 is smaller.
205,936 and 250,369: ten thousands: 0 and 5 are different. 0 < 5, so 205,936 is smaller.
250,369 and 250,639: hundreds: 3 and 6 are different. 3 < 6, so 250,369 is smaller. - Write them biggest first. Check you have used every number once.250,639, 250,369, 205,936, 205,639, 25,639
Check. Count the numbers: 5 in the question and 5 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Biggest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 418,000 4 1 8 0 0 0 481,000 4 8 1 0 0 0 4,180 4 1 8 0 408,100 4 0 8 1 0 0 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.4,180 and 408,100: 408,100 has 6 digits and 4,180 has 4 digits, so 408,100 is bigger.
408,100 and 418,000: ten thousands: 0 and 1 are different. 0 < 1, so 408,100 is smaller.
418,000 and 481,000: ten thousands: 1 and 8 are different. 1 < 8, so 418,000 is smaller. - Write them biggest first. Check you have used every number once.481,000, 418,000, 408,100, 4,180
Check. Count the numbers: 4 in the question and 4 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Method. Find out what each small mark is worth, then count on from a number you can read.
- Count the gaps between two labelled numbers. The line goes from 400,000 to 500,000 in 10 equal gaps.500,000 − 400,000 = 100,000
- Work out what one gap is worth. Share the distance equally between the gaps.100,000 ÷ 10 = 10,000
- Count on from the start to the arrow. The arrow is 7 gaps after 400,000.400,000 + 7 × 10,000 = 400,000 + 70,000 = 470,000
Check. Count back from 500,000: 3 gaps back is 500,000 − 30,000 = 470,000. ✓
Watch out. Do not read the nearest label. Count the small marks to find the exact number.
Method. Find out what each small mark is worth, then count on from a number you can read.
- Count the gaps between two labelled numbers. The line goes from 50,000 to 60,000 in 10 equal gaps.60,000 − 50,000 = 10,000
- Work out what one gap is worth. Share the distance equally between the gaps.10,000 ÷ 10 = 1,000
- Count on from the start to the arrow. The arrow is 7 gaps after 50,000.50,000 + 7 × 1,000 = 50,000 + 7,000 = 57,000
Check. Count back from 60,000: 3 gaps back is 60,000 − 3,000 = 57,000. ✓
Watch out. Do not read the nearest label. Count the small marks to find the exact number.
Method. Work out what each gap is worth. Then decide which two gaps the arrow is between and how far along it is.
- Work out what one gap is worth. The line goes from 0 to 1,000,000 in 10 equal gaps.1,000,000 ÷ 10 = 100,000
- Find the two numbers either side of the arrow. The arrow is after 2 gaps, but before 3 gaps.200,000 < arrow < 300,000
- Decide how far along the arrow is. Halfway between 200,000 and 300,000 is 250,000.The arrow is close to 250,000.
- Choose the best estimate. Pick the option nearest to the arrow.B (250,000)
Check. The other options are far away: 20,000, 520,000, 720,000. ✓
Watch out. An estimate is a sensible guess. You do not need the exact number.
4?5,200 > 435,200
Method. Try every digit from 0 to 9 in the box and compare each number with the number on the right. Compare from the left.
- Look at the columns that do not change. The hundred thousands digit is 4 in both numbers. The box is in the ten thousands column, so that is the next column to compare.The box digit must be bigger than 3.
- Try each digit. Write each number and compare it.405,200: less than 435,200
415,200: less than 435,200
425,200: less than 435,200
435,200: equal to 435,200
445,200: greater than 435,200 ✓
455,200: greater than 435,200 ✓
465,200: greater than 435,200 ✓
475,200: greater than 435,200 ✓
485,200: greater than 435,200 ✓
495,200: greater than 435,200 ✓ - Write the digits that work. Choose the numbers that are greater.4, 5, 6, 7, 8 and 9
Check. Digit 3 gives exactly 435,200, which is equal, not greater. The next digit is the first to work. ✓
Watch out. > means greater than. An equal number does not count.
Method. The number halfway between two numbers is the same distance from both. Find the gap between them, halve it, then add that to the smaller number.
- Find the gap between the two numbers. Subtract the smaller from the bigger.350,000 − 250,000 = 100,000
- Halve the gap. Halfway is half of the gap away from each number.100,000 ÷ 2 = 50,000
- Add half the gap to the smaller number. This moves us to the middle.250,000 + 50,000 = 300,000
Check. Another way: add the numbers and halve. 250,000 + 350,000 = 600,000 and 600,000 ÷ 2 = 300,000. ✓
Watch out. Halfway is not the average of the digits. Use the whole numbers.
Method. The number halfway between two numbers is the same distance from both. Find the gap between them, halve it, then add that to the smaller number.
- Find the gap between the two numbers. Subtract the smaller from the bigger.175,000 − 125,000 = 50,000
- Halve the gap. Halfway is half of the gap away from each number.50,000 ÷ 2 = 25,000
- Add half the gap to the smaller number. This moves us to the middle.125,000 + 25,000 = 150,000
Check. Another way: add the numbers and halve. 125,000 + 175,000 = 300,000 and 300,000 ÷ 2 = 150,000. ✓
Watch out. Halfway is not the average of the digits. Use the whole numbers.
Method. The number halfway between two numbers is the same distance from both. Find the gap between them, halve it, then add that to the smaller number.
- Find the gap between the two numbers. Subtract the smaller from the bigger.720,000 − 680,000 = 40,000
- Halve the gap. Halfway is half of the gap away from each number.40,000 ÷ 2 = 20,000
- Add half the gap to the smaller number. This moves us to the middle.680,000 + 20,000 = 700,000
Check. Another way: add the numbers and halve. 680,000 + 720,000 = 1,400,000 and 1,400,000 ÷ 2 = 700,000. ✓
Watch out. Halfway is not the average of the digits. Use the whole numbers.
Method. The number halfway between two numbers is the same distance from both. Find the gap between them, halve it, then add that to the smaller number.
- Find the gap between the two numbers. Subtract the smaller from the bigger.99,000 − 1,000 = 98,000
- Halve the gap. Halfway is half of the gap away from each number.98,000 ÷ 2 = 49,000
- Add half the gap to the smaller number. This moves us to the middle.1,000 + 49,000 = 50,000
Check. Another way: add the numbers and halve. 1,000 + 99,000 = 100,000 and 100,000 ÷ 2 = 50,000. ✓
Watch out. Halfway is not the average of the digits. Use the whole numbers.
Method. Think about which digit goes in the hundred thousands column, then the ten thousands, and so on. The biggest columns matter most.
- Put the digits in order, biggest first. The biggest digit in the biggest column makes the biggest number.9, 7, 5, 3, 2, 0
- Write them in that order. Biggest digit in the hundred thousands column, the next in the ten thousands, and so on.975,320
Check. Try swapping two digits. The new number is not bigger than 975,320. ✓
Watch out. A six-digit number cannot start with a zero.
Method. Think about which digit goes in the hundred thousands column, then the ten thousands, and so on. The biggest columns matter most.
- Put the digits in order, smallest first. The smallest digit in the biggest column makes the smallest number.0, 2, 3, 5, 7, 9
- Check the first digit. A six-digit number cannot start with 0, because then it would only have five digits. Use the smallest digit that is not 0 first, then put the 0 straight after it.First digit 2
- Write the number. 203,579
Check. Try swapping two digits. The new number is not smaller than 203,579. ✓
Watch out. A six-digit number cannot start with a zero.
Method. Think about which digit goes in the hundred thousands column, then the ten thousands, and so on. The biggest columns matter most.
- A number is even if its last digit (the ones digit) is even. Even digits are 0, 2, 4, 6, 8.Even digits here: 0, 2
- Try each possible ones digit. Make the rest of the number as small as possible each time. The other five digits go smallest first (but not starting with 0).Ones digit 0: smallest number is 235,790
Ones digit 2: smallest number is 305,792 - Choose the smallest of these numbers. Compare from the left.The smallest even number is 235,790.
Check. Try swapping two digits. The new number is not smaller than 235,790. ✓
Watch out. A six-digit number cannot start with a zero.
Method. Think about which digit goes in the hundred thousands column, then the ten thousands, and so on. The biggest columns matter most.
- Which digits can go first? The number must be less than 500,000, so the first digit must be smaller than 5 (and not 0).Possible first digits: 1, 2, 4
- Choose the biggest first digit. The first digit matters most.First digit = 4
- Put the other digits in order, biggest first. This makes the number as close to the limit as possible.4 then 8, 6, 2, 1, 0
- Write the number. 486,210
Check. Try swapping two digits. The new number is not bigger than 486,210. ✓
Watch out. A six-digit number cannot start with a zero.
Method. Think about which digit goes in the hundred thousands column, then the ten thousands, and so on. The biggest columns matter most.
- Which digits can go first? The number must be more than 500,000, so the first digit must be bigger than 5 (and not 0).Possible first digits: 6, 8
- Choose the smallest first digit. The first digit matters most.First digit = 6
- Put the other digits in order, smallest first. This makes the number as close to the limit as possible.6 then 0, 1, 2, 4, 8
- Write the number. 601,248
Check. Try swapping two digits. The new number is not smaller than 601,248. ✓
Watch out. A six-digit number cannot start with a zero.
| Town | People |
|---|---|
| Ashby | 185,420 |
| Bexley | 158,240 |
| Corton | 185,240 |
| Dunmore | 98,765 |
| Elford | 205,010 |
Method. Put the numbers in order and pick the one you need. Compare the numbers from the left.
- Write all the numbers in a place-value table. This lines them up.
Thousands Ones HTh TTh Th H T O 185,420 1 8 5 4 2 0 158,240 1 5 8 2 4 0 185,240 1 8 5 2 4 0 98,765 9 8 7 6 5 205,010 2 0 5 0 1 0 - Put them in order, biggest first. Compare column by column from the left.1. Elford: 205,010
2. Ashby: 185,420
3. Corton: 185,240
4. Bexley: 158,240
5. Dunmore: 98,765 - Pick the one with the most people. It is number 1 in the list.Elford (205,010)
Check. All the other numbers are smaller than 205,010 in the way we need. ✓
Watch out. Read the question again: is it the biggest, the smallest or the second biggest?
Method. Put the numbers in order and pick the one you need. Compare the numbers from the left.
- Write all the numbers in a place-value table. This lines them up.
Thousands Ones HTh TTh Th H T O 185,420 1 8 5 4 2 0 158,240 1 5 8 2 4 0 185,240 1 8 5 2 4 0 98,765 9 8 7 6 5 205,010 2 0 5 0 1 0 - Put them in order, smallest first. Compare column by column from the left.1. Dunmore: 98,765
2. Bexley: 158,240
3. Corton: 185,240
4. Ashby: 185,420
5. Elford: 205,010 - Pick the one with the fewest people. It is number 1 in the list.Dunmore (98,765)
Check. All the other numbers are different than 98,765 in the way we need. ✓
Watch out. Read the question again: is it the biggest, the smallest or the second biggest?
Method. Put the populations in descending order, then write the town names in that order.
- Put the populations in a place-value table. This lines up the digits.
Thousands Ones HTh TTh Th H T O 185,420 1 8 5 4 2 0 158,240 1 5 8 2 4 0 185,240 1 8 5 2 4 0 98,765 9 8 7 6 5 205,010 2 0 5 0 1 0 - Put them in order, biggest first. Compare from the left. 185,420 and 185,240 are the same until the hundreds column: 4 is more than 2.205,010 → Elford
185,420 → Ashby
185,240 → Corton
158,240 → Bexley
98,765 → Dunmore - Write the town names in that order. Elford, Ashby, Corton, Bexley, Dunmore
Check. There are 5 towns in the table and 5 in the answer. ✓
Watch out. Be careful with 185,420 and 185,240: they use the same digits but in different columns.
| Stadium | Seats |
|---|---|
| Arena A | 62,400 |
| Arena B | 59,250 |
| Arena C | 74,500 |
| Arena D | 60,000 |
Method. Put the numbers in order and pick the one you need. Compare the numbers from the left.
- Write all the numbers in a place-value table. This lines them up.
Thousands Ones TTh Th H T O 62,400 6 2 4 0 0 59,250 5 9 2 5 0 74,500 7 4 5 0 0 60,000 6 0 0 0 0 - Put them in order, biggest first. Compare column by column from the left.1. Arena C: 74,500
2. Arena A: 62,400
3. Arena D: 60,000
4. Arena B: 59,250 - Pick the one with the second most seats. It is number 2 in the list.Arena A (62,400)
Check. All the other numbers are different than 62,400 in the way we need. ✓
Watch out. Read the question again: is it the biggest, the smallest or the second biggest?
Method. Compare the two numbers properly, starting from the left. Then say what went wrong with Mei’s reasoning.
- Count the digits. 98,765 has 5 digits. 100,234 has 6 digits.A number with more digits is bigger.
- Compare the numbers. The six-digit number is bigger.98,765 < 100,234
- Say what Mei did wrong. She compared only the first digits (9 and 1). But the 1 in 100,234 is in the hundred thousands column and is worth 100,000, while the 9 in 98,765 is in the ten thousands column and is worth only 90,000.The first digit is worth different amounts because the numbers have different lengths.
Check. 100,234 − 98,765 = 1,469, so 100,234 is 1,469 more. ✓
Watch out. Always count the digits before you compare the first digits.
“If you swap two digits in a number, the new number is smaller.”
Method. Try swapping digits in a few numbers. If you find one that gets bigger and one that gets smaller, the answer is “sometimes”.
- Swap the first two digits of 123,456. The 1 and 2 swap.123,456 → 213,456. Is 213,456 bigger? Yes. It got bigger.
- Swap the first two digits of 654,321. The 6 and 5 swap.654,321 → 564,321. Is 564,321 smaller? Yes. It got smaller.
- Swap two digits that are the same in 440,000. The two 4s swap.440,000 stays 440,000. It did not change.
- Write the answer. It can get bigger, smaller or stay the same.Sometimes (it is not always smaller)
Check. Moving a bigger digit to a bigger column makes the number bigger. ✓
Watch out. One example is not enough to say “always”. Try to find an example that breaks the rule.
Method. Work out each multiplication, or divide the big number by the small number.
- Check Amira. Multiply 60,000 by 10.60,000 × 10 = 600,000 ✓
- Check Noah. Multiply 6,000 by 100.6,000 × 100 = 600,000 ✓
- Say who is right. Both statements work out to 600,000.Both Amira and Noah are right.
Check. On a place-value chart, the 6 moves one place left to go from 60,000 to 600,000 (10 times) and two places left from 6,000 (100 times). ✓
Watch out. Each place to the left makes a number 10 times bigger.
Method. The number must start with 4 or 5 to be close to 500,000. Find the closest number above and the closest below, then see which is nearer.
- Closest number above 500,000. It starts with 5. Put the other digits in order, smallest first, to stay as close to 500,000 as possible.5, then 1, 2, 3, 4, 6 → 512,346
512,346 − 500,000 = 12,346 - Closest number below 500,000. It starts with 4. Put the other digits in order, biggest first.4, then 6, 5, 3, 2, 1 → 465,321
500,000 − 465,321 = 34,679 - Compare the two gaps. The smaller gap is the closer number.12,346 < 34,679, so 512,346 is closer.
Check. Any other number is further away. For example 513,246 is 13,246 away. ✓
Watch out. Check numbers on both sides of 500,000. The closest number is not always above or always below.
Counting in steps of 10, 100, 1,000, 10,000 and 100,000
Printable: Worksheet (PDF) · Answers (PDF) · Open this lesson on its own page
The numbers 10, 100, 1,000, 10,000 and 100,000 are called powers of 10. Each one is 10 times bigger than the one before. When you count on or back in a power of 10, only one digit changes: the digit in the column with the same value as the step.
Count on in 10,000s from 253,400. Look at the table. The ten thousands digit goes up by 1 each time: 2, 3, 4, 5. The other digits stay the same.
| Thousands | Ones | |||||
|---|---|---|---|---|---|---|
| HTh | TTh | Th | H | T | O | |
| 253,400 | 2 | 5 | 3 | 4 | 0 | 0 |
| 263,400 | 2 | 6 | 3 | 4 | 0 | 0 |
| 273,400 | 2 | 7 | 3 | 4 | 0 | 0 |
| 283,400 | 2 | 8 | 3 | 4 | 0 | 0 |
Look out for 9s and 0s. When a digit is 9 and you add 1, it becomes 0 and you carry 1 to the next column. So 10,000 more than 395,000 is 405,000. When a digit is 0 and you take 1 away, you swap 1 from the next column for 10. So 1,000 less than 300,000 is 299,000. The swap can go along more than one column.
Missing numbers. To fill the gaps in a sequence, find two numbers you can see. Count the jumps between them, then divide the difference by the number of jumps. That tells you the size of each jump. To find how many jumps there are between two numbers, divide the difference by the size of one jump.
Key words. A sequence is a list of numbers that follows a rule. A power of 10 is 10, 100, 1,000, 10,000, 100,000 and so on. A term is one number in the sequence.
Key ideas
- Counting in a power of 10 changes only one digit: the one in the column with that value.
- A 9 going up carries 1 to the next column. A 0 going down swaps 1 from the next column.
- For 10 more or less, change the tens digit. For 100, the hundreds digit. For 1,000, 10,000 or 100,000, the thousands, ten thousands or hundred thousands digit.
- To find the step in a sequence: difference ÷ number of jumps.
- To find the number of jumps: total distance ÷ size of one jump.
Key words. Counting in steps of 100 means adding 100 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting on in 100s means adding 100 each time. Only the hundreds digit changes (unless we carry or swap).
- Find the size of each jump. We are counting on in steps of 100, which is 1 hundred.Each jump is +100.
- Work out the numbers one jump at a time. Always start from the number you have just found.3,450 + 100 = 3,550 (the hundreds digit goes 4 → 5)
3,550 + 100 = 3,650 (the hundreds digit goes 5 → 6)
3,650 + 100 = 3,750 (the hundreds digit goes 6 → 7)
3,750 + 100 = 3,850 (the hundreds digit goes 7 → 8) - Write the numbers in order. 3,550, 3,650, 3,750, 3,850
Check. Go the other way from the last number: 3,850 − 100 = 3,750. ✓
Watch out. Only the hundreds digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 1,000 means taking away 1,000 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting back in 1,000s means taking away 1,000 each time. Only the thousands digit changes (unless we carry or swap).
- Find the size of each jump. We are counting back in steps of 1,000, which is 1 thousand.Each jump is −1,000.
- Work out the numbers one jump at a time. Always start from the number you have just found.62,500 − 1,000 = 61,500 (the thousands digit goes 2 → 1)
61,500 − 1,000 = 60,500 (the thousands digit goes 1 → 0)
60,500 − 1,000 = 59,500 (0 thousands: swap 1 from the next column for 10 thousands, then take 1 thousand away)
59,500 − 1,000 = 58,500 (the thousands digit goes 9 → 8)
58,500 − 1,000 = 57,500 (the thousands digit goes 8 → 7) - Write the numbers in order. 61,500, 60,500, 59,500, 58,500, 57,500
Check. Go the other way from the last number: 57,500 + 1,000 = 58,500. ✓
Watch out. Only the thousands digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 100 means adding 100 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting on in 100s means adding 100 each time. Only the hundreds digit changes (unless we carry or swap).
- Find the size of each jump. We are counting on in steps of 100, which is 1 hundred.Each jump is +100.
- Work out the numbers one jump at a time. Always start from the number you have just found.98,600 + 100 = 98,700 (the hundreds digit goes 6 → 7)
98,700 + 100 = 98,800 (the hundreds digit goes 7 → 8)
98,800 + 100 = 98,900 (the hundreds digit goes 8 → 9)
98,900 + 100 = 99,000 (9 hundreds + 1 hundred = 10 hundreds: write 0 and carry 1 to the next column) - Write the numbers in order. 98,700, 98,800, 98,900, 99,000
Check. Go the other way from the last number: 99,000 − 100 = 98,900. ✓
Watch out. Only the hundreds digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 10,000 means taking away 10,000 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting back in 10,000s means taking away 10,000 each time. Only the ten thousands digit changes (unless we carry or swap).
- Find the size of each jump. We are counting back in steps of 10,000, which is 1 ten thousand.Each jump is −10,000.
- Work out the numbers one jump at a time. Always start from the number you have just found.205,000 − 10,000 = 195,000 (0 ten thousands: swap 1 from the next column for 10 ten thousands, then take 1 ten thousand away)
195,000 − 10,000 = 185,000 (the ten thousands digit goes 9 → 8)
185,000 − 10,000 = 175,000 (the ten thousands digit goes 8 → 7) - Write the numbers in order. 195,000, 185,000, 175,000
Check. Go the other way from the last number: 175,000 + 10,000 = 185,000. ✓
Watch out. Only the ten thousands digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Method. To find 100,000 more, change the hundred thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the hundred thousands digit. 100,000 is one hundred thousand, so we change the hundred thousands digit.
Thousands Ones HTh TTh Th H T O 4 7 8 3 5 0 - Add 1 to the hundred thousands digit. 100,000 more means 1 more hundred thousand.4 + 1 = 5 hundred thousands
- Write the new number. The digits that did not change stay the same.478,350 + 100,000 = 578,350
Check. Do the opposite: 578,350 − 100,000 = 478,350. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 1,000 less, change the thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the thousands digit. 1,000 is one thousand, so we change the thousands digit.
Thousands Ones HTh TTh Th H T O 3 0 0 0 0 0 - Take 1 from the thousands digit. There are 0 thousands, so we swap 1 from the next column for 10 thousands. If that next digit is also 0 we swap again. Then take 1 away.0 thousands → swap, then 10 − 1 = 9 thousands
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 300,000 3 0 0 0 0 0 299,000 2 9 9 0 0 0
300,000 − 1,000 = 299,000
Check. Do the opposite: 299,000 + 1,000 = 300,000. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. Find the size of one jump from two numbers you can see. Then use it to fill the gaps.
- Find two numbers you know and count the jumps between them. Each jump in the sequence is the same size.From 132,000 to 152,000 is 2 jumps.
The difference is 20,000.
20,000 ÷ 2 = 10,000 - Say which way and how big each jump is. The numbers are getting bigger, so we count on.Each jump is +10,000.
- Fill in the missing numbers. Add (or take away) one jump from a number you know. Where two gaps are side by side, fill one first and use it for the next.Number 2: 132,000 + 10,000 = 142,000
Number 4: 152,000 + 10,000 = 162,000 - Write the missing numbers. Put them in the order they appear.142,000, 162,000
Check. Read the whole sequence again and check every jump is +10,000: 132,000, 142,000, 152,000, 162,000, 172,000. ✓
Watch out. Do not just look at the first two numbers. Check the jump is the same all the way along.
Method. Work out how much each term changes by. If the jump is always the same, that is the rule.
- Write the first terms in a place-value table. Look for the one column that changes.
Thousands Ones TTh Th H T O 36,250 3 6 2 5 0 36,350 3 6 3 5 0 36,450 3 6 4 5 0 - Find the jump between two terms next to each other. The column that changes tells us the size of the jump.36,350 − 36,250 = 100 (it goes up)
- Check the jump is the same all the way along. A rule has to work for every pair of terms.36,350 − 36,250 = 100
36,450 − 36,350 = 100
36,550 − 36,450 = 100 - Write the rule and the next two terms. Add 100 each time.Rule: add 100.
Next two terms: 36,650, 36,750
Check. 36,550 + 100 = 36,650 and 36,650 + 100 = 36,750. ✓
Watch out. Check more than one pair of terms. One pair is not enough to be sure of the rule.
Method. Find the total distance, then work out how many jumps of 10,000 fit into it.
- Find how far it is from the start to the end. Subtract the start from the end.200,000 − 120,000 = 80,000
- Divide by the size of each jump. Each jump is 10,000.80,000 ÷ 10,000 = 8
- Write the answer. 8 jumps of 10,000
Check. 8 × 10,000 = 80,000 and 120,000 + 80,000 = 200,000. ✓
Watch out. Count the jumps, not the numbers you say. Counting the numbers would include the start and give one too many.
Watch out
Do not change every digit. 100,000 less than 640,000 is 540,000, not 630,000 or 539,000. Only the hundred thousands digit changes. Also take care with 9s and 0s: 1,000 less than 300,000 is 299,000, not 200,000.Exercise 1C Counting in powers of 10
Non-calculatorKey words. Counting in steps of 10 means adding 10 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting on in 10s means adding 10 each time. Only the tens digit changes (unless we carry or swap).
- Find the size of each jump. We are counting on in steps of 10, which is 1 ten.Each jump is +10.
- Work out the numbers one jump at a time. Always start from the number you have just found.4,570 + 10 = 4,580 (the tens digit goes 7 → 8)
4,580 + 10 = 4,590 (the tens digit goes 8 → 9)
4,590 + 10 = 4,600 (9 tens + 1 ten = 10 tens: write 0 and carry 1 to the next column) - Write the numbers in order. 4,580, 4,590, 4,600
Check. Go the other way from the last number: 4,600 − 10 = 4,590. ✓
Watch out. Only the tens digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 100 means adding 100 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting on in 100s means adding 100 each time. Only the hundreds digit changes (unless we carry or swap).
- Find the size of each jump. We are counting on in steps of 100, which is 1 hundred.Each jump is +100.
- Work out the numbers one jump at a time. Always start from the number you have just found.28,300 + 100 = 28,400 (the hundreds digit goes 3 → 4)
28,400 + 100 = 28,500 (the hundreds digit goes 4 → 5)
28,500 + 100 = 28,600 (the hundreds digit goes 5 → 6) - Write the numbers in order. 28,400, 28,500, 28,600
Check. Go the other way from the last number: 28,600 − 100 = 28,500. ✓
Watch out. Only the hundreds digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 1,000 means adding 1,000 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting on in 1,000s means adding 1,000 each time. Only the thousands digit changes (unless we carry or swap).
- Find the size of each jump. We are counting on in steps of 1,000, which is 1 thousand.Each jump is +1,000.
- Work out the numbers one jump at a time. Always start from the number you have just found.351,200 + 1,000 = 352,200 (the thousands digit goes 1 → 2)
352,200 + 1,000 = 353,200 (the thousands digit goes 2 → 3)
353,200 + 1,000 = 354,200 (the thousands digit goes 3 → 4) - Write the numbers in order. 352,200, 353,200, 354,200
Check. Go the other way from the last number: 354,200 − 1,000 = 353,200. ✓
Watch out. Only the thousands digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 10,000 means adding 10,000 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting on in 10,000s means adding 10,000 each time. Only the ten thousands digit changes (unless we carry or swap).
- Find the size of each jump. We are counting on in steps of 10,000, which is 1 ten thousand.Each jump is +10,000.
- Work out the numbers one jump at a time. Always start from the number you have just found.420,000 + 10,000 = 430,000 (the ten thousands digit goes 2 → 3)
430,000 + 10,000 = 440,000 (the ten thousands digit goes 3 → 4)
440,000 + 10,000 = 450,000 (the ten thousands digit goes 4 → 5) - Write the numbers in order. 430,000, 440,000, 450,000
Check. Go the other way from the last number: 450,000 − 10,000 = 440,000. ✓
Watch out. Only the ten thousands digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 10 means taking away 10 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting back in 10s means taking away 10 each time. Only the tens digit changes (unless we carry or swap).
- Find the size of each jump. We are counting back in steps of 10, which is 1 ten.Each jump is −10.
- Work out the numbers one jump at a time. Always start from the number you have just found.6,080 − 10 = 6,070 (the tens digit goes 8 → 7)
6,070 − 10 = 6,060 (the tens digit goes 7 → 6)
6,060 − 10 = 6,050 (the tens digit goes 6 → 5) - Write the numbers in order. 6,070, 6,060, 6,050
Check. Go the other way from the last number: 6,050 + 10 = 6,060. ✓
Watch out. Only the tens digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 100 means taking away 100 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting back in 100s means taking away 100 each time. Only the hundreds digit changes (unless we carry or swap).
- Find the size of each jump. We are counting back in steps of 100, which is 1 hundred.Each jump is −100.
- Work out the numbers one jump at a time. Always start from the number you have just found.71,450 − 100 = 71,350 (the hundreds digit goes 4 → 3)
71,350 − 100 = 71,250 (the hundreds digit goes 3 → 2)
71,250 − 100 = 71,150 (the hundreds digit goes 2 → 1) - Write the numbers in order. 71,350, 71,250, 71,150
Check. Go the other way from the last number: 71,150 + 100 = 71,250. ✓
Watch out. Only the hundreds digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 1,000 means taking away 1,000 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting back in 1,000s means taking away 1,000 each time. Only the thousands digit changes (unless we carry or swap).
- Find the size of each jump. We are counting back in steps of 1,000, which is 1 thousand.Each jump is −1,000.
- Work out the numbers one jump at a time. Always start from the number you have just found.530,000 − 1,000 = 529,000 (0 thousands: swap 1 from the next column for 10 thousands, then take 1 thousand away)
529,000 − 1,000 = 528,000 (the thousands digit goes 9 → 8)
528,000 − 1,000 = 527,000 (the thousands digit goes 8 → 7) - Write the numbers in order. 529,000, 528,000, 527,000
Check. Go the other way from the last number: 527,000 + 1,000 = 528,000. ✓
Watch out. Only the thousands digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. Counting in steps of 100,000 means taking away 100,000 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting back in 100,000s means taking away 100,000 each time. Only the hundred thousands digit changes (unless we carry or swap).
- Find the size of each jump. We are counting back in steps of 100,000, which is 1 hundred thousand.Each jump is −100,000.
- Work out the numbers one jump at a time. Always start from the number you have just found.900,000 − 100,000 = 800,000 (the hundred thousands digit goes 9 → 8)
800,000 − 100,000 = 700,000 (the hundred thousands digit goes 8 → 7)
700,000 − 100,000 = 600,000 (the hundred thousands digit goes 7 → 6) - Write the numbers in order. 800,000, 700,000, 600,000
Check. Go the other way from the last number: 600,000 + 100,000 = 700,000. ✓
Watch out. Only the hundred thousands digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Method. To find 10 more, change the tens digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the tens digit. 10 is one ten, so we change the tens digit.
Thousands Ones Th H T O 7 9 9 5 - Add 1 to the tens digit. There are 9 tens. 1 more ten makes 10 tens, which is 1 of the next column and 0 tens. We carry (and the carry carries on if the next digit is also 9).9 + 1 = 10 → write 0 in the T column and carry 1
- Write the new number. The digits that did not change stay the same.
Thousands Ones Th H T O 7,995 7 9 9 5 8,005 8 0 0 5
7,995 + 10 = 8,005
Check. Do the opposite: 8,005 − 10 = 7,995. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 100 more, change the hundreds digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the hundreds digit. 100 is one hundred, so we change the hundreds digit.
Thousands Ones TTh Th H T O 5 4 9 5 0 - Add 1 to the hundreds digit. There are 9 hundreds. 1 more hundred makes 10 hundreds, which is 1 of the next column and 0 hundreds. We carry (and the carry carries on if the next digit is also 9).9 + 1 = 10 → write 0 in the H column and carry 1
- Write the new number. The digits that did not change stay the same.
Thousands Ones TTh Th H T O 54,950 5 4 9 5 0 55,050 5 5 0 5 0
54,950 + 100 = 55,050
Check. Do the opposite: 55,050 − 100 = 54,950. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 1,000 more, change the thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the thousands digit. 1,000 is one thousand, so we change the thousands digit.
Thousands Ones HTh TTh Th H T O 2 4 9 5 0 0 - Add 1 to the thousands digit. There are 9 thousands. 1 more thousand makes 10 thousands, which is 1 of the next column and 0 thousands. We carry (and the carry carries on if the next digit is also 9).9 + 1 = 10 → write 0 in the Th column and carry 1
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 249,500 2 4 9 5 0 0 250,500 2 5 0 5 0 0
249,500 + 1,000 = 250,500
Check. Do the opposite: 250,500 − 1,000 = 249,500. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 10,000 more, change the ten thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the ten thousands digit. 10,000 is one ten thousand, so we change the ten thousands digit.
Thousands Ones HTh TTh Th H T O 3 9 5 0 0 0 - Add 1 to the ten thousands digit. There are 9 ten thousands. 1 more ten thousand makes 10 ten thousands, which is 1 of the next column and 0 ten thousands. We carry (and the carry carries on if the next digit is also 9).9 + 1 = 10 → write 0 in the TTh column and carry 1
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 395,000 3 9 5 0 0 0 405,000 4 0 5 0 0 0
395,000 + 10,000 = 405,000
Check. Do the opposite: 405,000 − 10,000 = 395,000. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 100,000 more, change the hundred thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the hundred thousands digit. 100,000 is one hundred thousand, so we change the hundred thousands digit.
Thousands Ones HTh TTh Th H T O 2 9 9 9 9 9 - Add 1 to the hundred thousands digit. 100,000 more means 1 more hundred thousand.2 + 1 = 3 hundred thousands
- Write the new number. The digits that did not change stay the same.299,999 + 100,000 = 399,999
Check. Do the opposite: 399,999 − 100,000 = 299,999. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 10,000 more, change the ten thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the ten thousands digit. 10,000 is one ten thousand, so we change the ten thousands digit.
Thousands Ones HTh TTh Th H T O 8 9 9 0 0 0 - Add 1 to the ten thousands digit. There are 9 ten thousands. 1 more ten thousand makes 10 ten thousands, which is 1 of the next column and 0 ten thousands. We carry (and the carry carries on if the next digit is also 9).9 + 1 = 10 → write 0 in the TTh column and carry 1
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 899,000 8 9 9 0 0 0 909,000 9 0 9 0 0 0
899,000 + 10,000 = 909,000
Check. Do the opposite: 909,000 − 10,000 = 899,000. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 10 less, change the tens digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the tens digit. 10 is one ten, so we change the tens digit.
Thousands Ones Th H T O 5 0 0 0 - Take 1 from the tens digit. There are 0 tens, so we swap 1 from the next column for 10 tens. If that next digit is also 0 we swap again. Then take 1 away.0 tens → swap, then 10 − 1 = 9 tens
- Write the new number. The digits that did not change stay the same.
Thousands Ones Th H T O 5,000 5 0 0 0 4,990 4 9 9 0
5,000 − 10 = 4,990
Check. Do the opposite: 4,990 + 10 = 5,000. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 100 less, change the hundreds digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the hundreds digit. 100 is one hundred, so we change the hundreds digit.
Thousands Ones TTh Th H T O 3 0 0 5 0 - Take 1 from the hundreds digit. There are 0 hundreds, so we swap 1 from the next column for 10 hundreds. If that next digit is also 0 we swap again. Then take 1 away.0 hundreds → swap, then 10 − 1 = 9 hundreds
- Write the new number. The digits that did not change stay the same.
Thousands Ones TTh Th H T O 30,050 3 0 0 5 0 29,950 2 9 9 5 0
30,050 − 100 = 29,950
Check. Do the opposite: 29,950 + 100 = 30,050. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 1,000 less, change the thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the thousands digit. 1,000 is one thousand, so we change the thousands digit.
Thousands Ones HTh TTh Th H T O 1 0 0 0 0 0 - Take 1 from the thousands digit. There are 0 thousands, so we swap 1 from the next column for 10 thousands. If that next digit is also 0 we swap again. Then take 1 away.0 thousands → swap, then 10 − 1 = 9 thousands
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 100,000 1 0 0 0 0 0 99,000 9 9 0 0 0
100,000 − 1,000 = 99,000
Check. Do the opposite: 99,000 + 1,000 = 100,000. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 10,000 less, change the ten thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the ten thousands digit. 10,000 is one ten thousand, so we change the ten thousands digit.
Thousands Ones HTh TTh Th H T O 2 0 5 0 0 0 - Take 1 from the ten thousands digit. There are 0 ten thousands, so we swap 1 from the next column for 10 ten thousands. If that next digit is also 0 we swap again. Then take 1 away.0 ten thousands → swap, then 10 − 1 = 9 ten thousands
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 205,000 2 0 5 0 0 0 195,000 1 9 5 0 0 0
205,000 − 10,000 = 195,000
Check. Do the opposite: 195,000 + 10,000 = 205,000. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 100,000 less, change the hundred thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the hundred thousands digit. 100,000 is one hundred thousand, so we change the hundred thousands digit.
Thousands Ones HTh TTh Th H T O 6 4 0 0 0 0 - Take 1 from the hundred thousands digit. 100,000 less means 1 less hundred thousand.6 − 1 = 5 hundred thousands
- Write the new number. The digits that did not change stay the same.640,000 − 100,000 = 540,000
Check. Do the opposite: 540,000 + 100,000 = 640,000. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 1,000 less, change the thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the thousands digit. 1,000 is one thousand, so we change the thousands digit.
Thousands Ones HTh TTh Th H T O 7 0 0 5 0 0 - Take 1 from the thousands digit. There are 0 thousands, so we swap 1 from the next column for 10 thousands. If that next digit is also 0 we swap again. Then take 1 away.0 thousands → swap, then 10 − 1 = 9 thousands
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 700,500 7 0 0 5 0 0 699,500 6 9 9 5 0 0
700,500 − 1,000 = 699,500
Check. Do the opposite: 699,500 + 1,000 = 700,500. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. Find the size of one jump from two numbers you can see. Then use it to fill the gaps.
- Find two numbers you know and count the jumps between them. Each jump in the sequence is the same size.From 7,260 to 7,270 is 1 jump.
The difference is 10. - Say which way and how big each jump is. The numbers are getting bigger, so we count on.Each jump is +10.
- Fill in the missing numbers. Add (or take away) one jump from a number you know. Where two gaps are side by side, fill one first and use it for the next.Number 1: 7,260 − 10 = 7,250
Number 4: 7,270 + 10 = 7,280 - Write the missing numbers. Put them in the order they appear.7,250, 7,280
Check. Read the whole sequence again and check every jump is +10: 7,250, 7,260, 7,270, 7,280, 7,290. ✓
Watch out. Do not just look at the first two numbers. Check the jump is the same all the way along.
Method. Find the size of one jump from two numbers you can see. Then use it to fill the gaps.
- Find two numbers you know and count the jumps between them. Each jump in the sequence is the same size.From 850,000 to 550,000 is 3 jumps.
The difference is 300,000.
300,000 ÷ 3 = 100,000 - Say which way and how big each jump is. The numbers are getting smaller, so we count back.Each jump is −100,000.
- Fill in the missing numbers. Add (or take away) one jump from a number you know. Where two gaps are side by side, fill one first and use it for the next.Number 2: 850,000 − 100,000 = 750,000
Number 3: 750,000 − 100,000 = 650,000 - Write the missing numbers. Put them in the order they appear.750,000, 650,000
Check. Read the whole sequence again and check every jump is −100,000: 850,000, 750,000, 650,000, 550,000, 450,000. ✓
Watch out. Do not just look at the first two numbers. Check the jump is the same all the way along.
Method. Find the size of one jump from two numbers you can see. Then use it to fill the gaps.
- Find two numbers you know and count the jumps between them. Each jump in the sequence is the same size.From 395,000 to 397,000 is 2 jumps.
The difference is 2,000.
2,000 ÷ 2 = 1,000 - Say which way and how big each jump is. The numbers are getting bigger, so we count on.Each jump is +1,000.
- Fill in the missing numbers. Add (or take away) one jump from a number you know. Where two gaps are side by side, fill one first and use it for the next.Number 2: 395,000 + 1,000 = 396,000
Number 5: 398,000 + 1,000 = 399,000
Number 6: 399,000 + 1,000 = 400,000 - Write the missing numbers. Put them in the order they appear.396,000, 399,000, 400,000
Check. Read the whole sequence again and check every jump is +1,000: 395,000, 396,000, 397,000, 398,000, 399,000, 400,000. ✓
Watch out. Do not just look at the first two numbers. Check the jump is the same all the way along.
Method. Find the size of one jump from two numbers you can see. Then use it to fill the gaps.
- Find two numbers you know and count the jumps between them. Each jump in the sequence is the same size.From 600,000 to 800,000 is 2 jumps.
The difference is 200,000.
200,000 ÷ 2 = 100,000 - Say which way and how big each jump is. The numbers are getting bigger, so we count on.Each jump is +100,000.
- Fill in the missing numbers. Add (or take away) one jump from a number you know. Where two gaps are side by side, fill one first and use it for the next.Number 2: 600,000 + 100,000 = 700,000
Number 4: 800,000 + 100,000 = 900,000 - Write the missing numbers. Put them in the order they appear.700,000, 900,000
Check. Read the whole sequence again and check every jump is +100,000: 600,000, 700,000, 800,000, 900,000, 1,000,000. ✓
Watch out. Do not just look at the first two numbers. Check the jump is the same all the way along.
Method. Find the size of one jump from two numbers you can see. Then use it to fill the gaps.
- Find two numbers you know and count the jumps between them. Each jump in the sequence is the same size.From 4,000 to 3,700 is 3 jumps.
The difference is 300.
300 ÷ 3 = 100 - Say which way and how big each jump is. The numbers are getting smaller, so we count back.Each jump is −100.
- Fill in the missing numbers. Add (or take away) one jump from a number you know. Where two gaps are side by side, fill one first and use it for the next.Number 2: 4,000 − 100 = 3,900
Number 3: 3,900 − 100 = 3,800 - Write the missing numbers. Put them in the order they appear.3,900, 3,800
Check. Read the whole sequence again and check every jump is −100: 4,000, 3,900, 3,800, 3,700. ✓
Watch out. Do not just look at the first two numbers. Check the jump is the same all the way along.
Method. Find the size of one jump from two numbers you can see. Then use it to fill the gaps.
- Find two numbers you know and count the jumps between them. Each jump in the sequence is the same size.From 240,000 to 270,000 is 3 jumps.
The difference is 30,000.
30,000 ÷ 3 = 10,000 - Say which way and how big each jump is. The numbers are getting bigger, so we count on.Each jump is +10,000.
- Fill in the missing numbers. Add (or take away) one jump from a number you know. Where two gaps are side by side, fill one first and use it for the next.Number 2: 240,000 + 10,000 = 250,000
Number 3: 250,000 + 10,000 = 260,000
Number 6: 280,000 + 10,000 = 290,000
Number 8: 300,000 + 10,000 = 310,000 - Write the missing numbers. Put them in the order they appear.250,000, 260,000, 290,000, 310,000
Check. Read the whole sequence again and check every jump is +10,000: 240,000, 250,000, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320,000. ✓
Watch out. Do not just look at the first two numbers. Check the jump is the same all the way along.
Method. Work out how much each term changes by. If the jump is always the same, that is the rule.
- Write the first terms in a place-value table. Look for the one column that changes.
Thousands Ones Th H T O 5,320 5 3 2 0 5,420 5 4 2 0 5,520 5 5 2 0 - Find the jump between two terms next to each other. The column that changes tells us the size of the jump.5,420 − 5,320 = 100 (it goes up)
- Check the jump is the same all the way along. A rule has to work for every pair of terms.5,420 − 5,320 = 100
5,520 − 5,420 = 100
5,620 − 5,520 = 100 - Write the rule and the next two terms. Add 100 each time.Rule: add 100.
Next two terms: 5,720, 5,820
Check. 5,620 + 100 = 5,720 and 5,720 + 100 = 5,820. ✓
Watch out. Check more than one pair of terms. One pair is not enough to be sure of the rule.
Method. Work out how much each term changes by. If the jump is always the same, that is the rule.
- Write the first terms in a place-value table. Look for the one column that changes.
Thousands Ones HTh TTh Th H T O 800,000 8 0 0 0 0 0 700,000 7 0 0 0 0 0 600,000 6 0 0 0 0 0 - Find the jump between two terms next to each other. The column that changes tells us the size of the jump.800,000 − 700,000 = 100,000 (it goes down)
- Check the jump is the same all the way along. A rule has to work for every pair of terms.800,000 − 700,000 = 100,000
700,000 − 600,000 = 100,000
600,000 − 500,000 = 100,000 - Write the rule and the next two terms. Subtract 100,000 each time.Rule: subtract 100,000.
Next two terms: 400,000, 300,000
Check. 500,000 − 100,000 = 400,000 and 400,000 − 100,000 = 300,000. ✓
Watch out. Check more than one pair of terms. One pair is not enough to be sure of the rule.
Method. Work out how much each term changes by. If the jump is always the same, that is the rule.
- Write the first terms in a place-value table. Look for the one column that changes.
Thousands Ones HTh TTh Th H T O 204,000 2 0 4 0 0 0 214,000 2 1 4 0 0 0 224,000 2 2 4 0 0 0 - Find the jump between two terms next to each other. The column that changes tells us the size of the jump.214,000 − 204,000 = 10,000 (it goes up)
- Check the jump is the same all the way along. A rule has to work for every pair of terms.214,000 − 204,000 = 10,000
224,000 − 214,000 = 10,000
234,000 − 224,000 = 10,000 - Write the rule and the next two terms. Add 10,000 each time.Rule: add 10,000.
Next two terms: 244,000, 254,000
Check. 234,000 + 10,000 = 244,000 and 244,000 + 10,000 = 254,000. ✓
Watch out. Check more than one pair of terms. One pair is not enough to be sure of the rule.
Method. Work out how much each term changes by. If the jump is always the same, that is the rule.
- Write the first terms in a place-value table. Look for the one column that changes.
Thousands Ones Th H T O 8,090 8 0 9 0 8,080 8 0 8 0 8,070 8 0 7 0 - Find the jump between two terms next to each other. The column that changes tells us the size of the jump.8,090 − 8,080 = 10 (it goes down)
- Check the jump is the same all the way along. A rule has to work for every pair of terms.8,090 − 8,080 = 10
8,080 − 8,070 = 10
8,070 − 8,060 = 10 - Write the rule and the next two terms. Subtract 10 each time.Rule: subtract 10.
Next two terms: 8,050, 8,040
Check. 8,060 − 10 = 8,050 and 8,050 − 10 = 8,040. ✓
Watch out. Check more than one pair of terms. One pair is not enough to be sure of the rule.
Method. Look at the two numbers in the number sentence. Find which column changes, or use the opposite (inverse) operation, to find the missing number.
- Look at the number sentence. The box stands for the number we want.245,600 + ? = 345,600
- Put the two known numbers in a place-value table. Only one column changes, and it shows the size of the jump.
Thousands Ones HTh TTh Th H T O 245,600 2 4 5 6 0 0 345,600 3 4 5 6 0 0 - Work out the missing number. Use the opposite operation to check the size of the change.345,600 − 245,600 = 100,000
- Check it in the number sentence. Put the answer back in the box.245,600 + 100,000 = 345,600 ✓
Check. The change is 100,000, a power of 10 (or a number made from powers of 10). ✓
Watch out. The box is not always at the start. Think about what the sentence is saying before you choose + or −.
Method. Look at the two numbers in the number sentence. Find which column changes, or use the opposite (inverse) operation, to find the missing number.
- Look at the number sentence. The box stands for the number we want.? − 1,000 = 87,500
- Put the two known numbers in a place-value table. Only one column changes, and it shows the size of the jump.
Thousands Ones TTh Th H T O 87,500 8 7 5 0 0 88,500 8 8 5 0 0 - Work out the missing number. Use the opposite operation to check the size of the change.87,500 + 1,000 = 88,500
- Check it in the number sentence. Put the answer back in the box.88,500 − 1,000 = 87,500 ✓
Check. The change is 1,000, a power of 10 (or a number made from powers of 10). ✓
Watch out. The box is not always at the start. Think about what the sentence is saying before you choose + or −.
Method. Look at the two numbers in the number sentence. Find which column changes, or use the opposite (inverse) operation, to find the missing number.
- Look at the number sentence. The box stands for the number we want.630,000 − ? = 620,000
- Put the two known numbers in a place-value table. Only one column changes, and it shows the size of the jump.
Thousands Ones HTh TTh Th H T O 620,000 6 2 0 0 0 0 630,000 6 3 0 0 0 0 - Work out the missing number. Use the opposite operation to check the size of the change.630,000 − 620,000 = 10,000
- Check it in the number sentence. Put the answer back in the box.630,000 − 10,000 = 620,000 ✓
Check. The change is 10,000, a power of 10 (or a number made from powers of 10). ✓
Watch out. The box is not always at the start. Think about what the sentence is saying before you choose + or −.
Method. Look at the two numbers in the number sentence. Find which column changes, or use the opposite (inverse) operation, to find the missing number.
- Look at the number sentence. The box stands for the number we want.? + 100 = 4,000
- Put the two known numbers in a place-value table. Only one column changes, and it shows the size of the jump.
Thousands Ones Th H T O 3,900 3 9 0 0 4,000 4 0 0 0 - Work out the missing number. Use the opposite operation to check the size of the change.4,000 − 100 = 3,900
- Check it in the number sentence. Put the answer back in the box.3,900 + 100 = 4,000 ✓
Check. The change is 100, a power of 10 (or a number made from powers of 10). ✓
Watch out. The box is not always at the start. Think about what the sentence is saying before you choose + or −.
Method. Add 10,000 for each day. Stop when the number is more than 100,000.
- Start with the views now. This is day 0.Day 0: 48,500
- Add 10,000 each day. Only the ten thousands digit changes (and a carry when it passes 9).Day 1: 48,500 + 10,000 = 58,500
Day 2: 58,500 + 10,000 = 68,500
Day 3: 68,500 + 10,000 = 78,500
Day 4: 78,500 + 10,000 = 88,500
Day 5: 88,500 + 10,000 = 98,500
Day 6: 98,500 + 10,000 = 108,500 - Find the first number over 100,000. Day 5 has 98,500, which is still less than 100,000. Day 6 has 108,500.Day 6
Check. 48,500 + 6 × 10,000 = 108,500, which is more than 100,000. ✓
Watch out. The number has to be more than 100,000. Make sure you do not stop at 98,500 (day 5).
Method. Find the total distance, then work out how many jumps of 10,000 fit into it.
- Find how far it is from the start to the end. Subtract the start from the end.200,000 − 120,000 = 80,000
- Divide by the size of each jump. Each jump is 10,000.80,000 ÷ 10,000 = 8
- Write the answer. 8 jumps of 10,000
Check. 8 × 10,000 = 80,000 and 120,000 + 80,000 = 200,000. ✓
Watch out. Count the jumps, not the numbers you say. Counting the numbers would include the start and give one too many.
Method. Find the total distance, then work out how many jumps of 100 fit into it.
- Find how far it is from the start to the end. Subtract the start from the end.4,200 − 3,500 = 700
- Divide by the size of each jump. Each jump is 100.700 ÷ 100 = 7
- Write the answer. 7 jumps of 100
Check. 7 × 100 = 700 and 3,500 + 700 = 4,200. ✓
Watch out. Count the jumps, not the numbers you say. Counting the numbers would include the start and give one too many.
Method. Find the total distance, then work out how many jumps of 100,000 fit into it.
- Find how far it is from the start to the end. Subtract the start from the end.650,000 − 150,000 = 500,000
- Divide by the size of each jump. Each jump is 100,000.500,000 ÷ 100,000 = 5
- Write the answer. 5 jumps of 100,000
Check. 5 × 100,000 = 500,000 and 150,000 + 500,000 = 650,000. ✓
Watch out. Count the jumps, not the numbers you say. Counting the numbers would include the start and give one too many.
Method. To find 10 more, change the tens digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the tens digit. 10 is one ten, so we change the tens digit.
Thousands Ones TTh Th H T O 9 9 9 9 5 - Add 1 to the tens digit. There are 9 tens. 1 more ten makes 10 tens, which is 1 of the next column and 0 tens. We carry (and the carry carries on if the next digit is also 9).9 + 1 = 10 → write 0 in the T column and carry 1
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 99,995 9 9 9 9 5 100,005 1 0 0 0 0 5
99,995 + 10 = 100,005
Check. Do the opposite: 100,005 − 10 = 99,995. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. To find 100 more, change the hundreds digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the hundreds digit. 100 is one hundred, so we change the hundreds digit.
Thousands Ones TTh Th H T O 4 9 9 5 0 - Add 1 to the hundreds digit. There are 9 hundreds. 1 more hundred makes 10 hundreds, which is 1 of the next column and 0 hundreds. We carry (and the carry carries on if the next digit is also 9).9 + 1 = 10 → write 0 in the H column and carry 1
- Write the new number. The digits that did not change stay the same.
Thousands Ones TTh Th H T O 49,950 4 9 9 5 0 50,050 5 0 0 5 0
49,950 + 100 = 50,050
Check. Do the opposite: 50,050 − 100 = 49,950. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. Count back in 1,000s, one minute at a time. Each minute is one jump.
- Say what each jump is. Each minute, the amount goes down by 1,000.1 minute = −1,000
- Count 7 jumps. Start each jump from the number you have just found.Minute 1: 25,000 − 1,000 = 24,000
Minute 2: 24,000 − 1,000 = 23,000
Minute 3: 23,000 − 1,000 = 22,000
Minute 4: 22,000 − 1,000 = 21,000
Minute 5: 21,000 − 1,000 = 20,000
Minute 6: 20,000 − 1,000 = 19,000
Minute 7: 19,000 − 1,000 = 18,000 - Write the answer. 18,000 litres
Check. 7 × 1,000 = 7,000 and 25,000 − 7,000 = 18,000. ✓
Watch out. Count the jumps carefully. Tally marks can help you keep track.
Method. The tank is empty when all 25,000 litres have gone. Find how many lots of 1,000 litres are in 25,000.
- Find the amount to drain. The whole tank.25,000 litres
- Divide by the amount that drains each minute. Each minute is 1,000 litres.25,000 ÷ 1,000 = 25
- Write the answer. 25 minutes
Check. 25 × 1,000 = 25,000. ✓
Watch out. Count the minutes, not the litres.
Method. Work out 1,000 less than 300,000 yourself, then compare it with Sam’s answer.
- Put 300,000 in a place-value table. The thousands digit is 0.
Thousands Ones HTh TTh Th H T O 3 0 0 0 0 0 - Take 1,000 away. There are 0 thousands, so we swap 1 hundred thousand for 10 ten thousands, then 1 ten thousand for 10 thousands. Then take 1 thousand away.300,000 − 1,000 = 299,000
- Say what Sam did. Sam wrote 200,000. That is 300,000 − 100,000, so he took away 100,000 instead of 1,000.He changed the hundred thousands digit instead of the thousands digit.
Check. 299,000 + 1,000 = 300,000. ✓
Watch out. Change the digit in the column that matches the step: 1,000 means the thousands column.
“When you add 1,000 to a number, only the thousands digit changes.”
Method. Try adding 1,000 to some numbers. Look at which digits change.
- Try 342,150. The thousands digit is 2.342,150 + 1,000 = 343,150. Only the thousands digit changed. It works.
- Try 349,150. The thousands digit is 9, so we carry.349,150 + 1,000 = 350,150. The thousands, ten thousands digits changed. It does not work.
- Write the answer. It works when the thousands digit is not 9.Sometimes
Check. It only fails when the thousands digit is 9. ✓
Watch out. 9s are the problem: adding to a 9 carries to the next column.
Method. Write out the numbers she says and see whether 100,000 is one of them.
- Count on in 10,000s from 5,000. Add 10,000 each time.5,000, 15,000, 25,000, 35,000, 45,000, 55,000, 65,000, 75,000, 85,000, 95,000, 105,000
- Look for 100,000. She goes from 95,000 to 105,000, so she jumps over it.95,000 < 100,000 < 105,000
- Explain why. Every number she says ends in 5,000, but 100,000 ends in 0,000.No, she will not say 100,000.
Check. 100,000 − 5,000 = 95,000, and 95,000 ÷ 10,000 = 9.5, which is not a whole number of jumps. ✓
Watch out. A number is only in the sequence if you can reach it with a whole number of jumps.
Method. Find how many jumps of 1,000 are needed to get past 50,000. Then work out the number.
- Find how far 7,125 is from 50,000. Subtract.50,000 − 7,125 = 42,875
- Divide by the size of each jump. This tells us how many whole jumps fit before 50,000.42,875 ÷ 1,000 = 42 remainder 875
So 42 jumps are not enough (we land on 49,125). We need 43 jumps. - Count 43 jumps. The last few numbers show it going over.47,125, 48,125, 49,125, 50,125
- Write the answer. 50,125 after 43 jumps
Check. 7,125 + 43 × 1,000 = 50,125, which is more than 50,000. ✓
Watch out. The number must be more than 50,000.
Negative numbers: temperatures, depths and bank balances
Printable: Worksheet (PDF) · Answers (PDF) · Open this lesson on its own page
Numbers below zero are called negative numbers. We use them in real life. When it is very cold, the temperature can go below zero: 5 degrees below zero is written −5°C. When we measure heights and depths, sea level is zero. A diver 15 metres under the sea is at −15 m. In a bank account, a balance of −£30 means the account is overdrawn: you owe the bank £30. In a building, floors below the ground floor can be −1, −2 and so on.
On a number line, zero is in the middle. Numbers to the right are bigger. Numbers to the left are smaller, so the further left a number is, the smaller it is. −20 is smaller than −5.
Counting through zero. If you count back in 4s from 10, you say 6, 2, −2, −6… When a jump goes past zero, split it into two parts. To work out 2 − 4, go down 2 to reach 0, then 2 more: that is −2. Going up works the same way: −3 + 7 is 3 up to reach 0, then 4 more, which is 4.
The difference across zero. To find how far apart a negative and a positive number are, add their distances from zero. From −9 up to 6 is 9 + 6 = 15. If both numbers are below zero, take the smaller distance from the bigger: from −9 to −2 is 9 − 2 = 7.
Key words. A negative number is less than zero. Overdrawn means the bank balance is below zero. The difference between two numbers is how far apart they are on a number line.
Key ideas
- Negative numbers are less than zero: −1, −2, −3… Used for temperatures, depths below sea level, overdrawn bank balances and floors below ground.
- On a number line, the further left, the smaller. −20 < −5.
- Counting through zero: split the jump into the part that reaches 0 and the part that goes past it.
- Difference across zero: add the distances from zero (−9 to 6 is 9 + 6 = 15).
- Difference when both are below zero: subtract the distances (−9 to −2 is 9 − 2 = 7).
Method. Find the numbered mark nearest the top of the red liquid, then count the small marks to the top.
- Look at the numbers on the scale. The scale is numbered every 5 degrees. The small marks are 1 degree each.Big numbers: ..., −5, 0, 5, 10, ...
- Find the numbered mark just below the top of the red. The top of the red is between −10 and −5.The mark below is −10.
- Count the small marks above it. Each small mark is 1 degree.3 small marks above −10: −10 + 3 = −7
Check. Count from 0 instead: the top of the red is 7 small marks below 0, so the temperature is −7°C. ✓
Watch out. Going up the scale the numbers get bigger. Below zero, the number nearest the bottom is the smallest.
Key words. A negative number is less than zero. It has a minus sign in front, like −4.
Method. Counting back in 4s means taking away 4 each time. A number line helps when we go through zero.
- Draw a number line. Numbers to the left of 0 are negative (below zero). Numbers to the right are positive.
- Jump back 4 each time, starting from 14. When a jump goes past zero, split it into the part that reaches zero and the part that goes beyond.14 − 4 = 10
10 − 4 = 6
6 − 4 = 2
2 down 4: go down 2 to reach 0, then 2 more below zero → −2
−2 down 4: start at or below zero and go down 4 more → −6
−6 down 4: start at or below zero and go down 4 more → −10 - Write the numbers in order. 10, 6, 2, −2, −6, −10
Check. Go the other way from the last number: −10 + 4 = −6. ✓
Watch out. After 0 comes −1, not 1. Below zero the numbers count down: −1, −2, −3…
Key words. A negative number is less than zero. It has a minus sign in front, like −4.
Method. Counting on in 10s means adding 10 each time. A number line helps when we go through zero.
- Draw a number line. Numbers to the left of 0 are negative (below zero). Numbers to the right are positive.
- Jump on 10 each time, starting from −35. When a jump goes past zero, split it into the part that reaches zero and the part that goes beyond.−35 up 10: start below zero and go up 10 → −25
−25 up 10: start below zero and go up 10 → −15
−15 up 10: start below zero and go up 10 → −5
−5 up 10: go up 5 to reach 0, then 5 more → 5
5 + 10 = 15 - Write the numbers in order. −25, −15, −5, 5, 15
Check. Go the other way from the last number: 15 − 10 = 5. ✓
Watch out. After 0 comes −1, not 1. Below zero the numbers count down: −1, −2, −3…
Method. Draw a number line, start at 5 and jump down 12. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 12. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.5 down 12: go down 5 to reach 0, then 7 more below zero → −7
- Write the answer. This is the new temperature.−7°C
Check. Do the opposite: −7 + 12 = 5. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. Draw a number line, start at −9 and jump up 14. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go up 14. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.−9 up 14: go up 9 to reach 0, then 5 more → 5
- Write the answer. This is the new temperature.5°C
Check. Do the opposite: 5 − 14 = −9. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−9 up to 0 is 9.
0 up to 6 is 6.
9 + 6 = 15 - Write the answer. 15°C
Check. Start at −9 and go up 15: −9 + 15 = 6. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. On a number line, numbers further to the left are smaller. Mark each number, then read them off from left to right.
- Put the numbers on a number line. The line shows which are below zero.
- Read from left to right. Left is smallest, right is biggest.−20, −12, −3, 0, 5, 8
- Write them smallest first. Check you have used every number once.−20, −12, −3, 0, 5, 8
Check. The numbers below zero are the smallest. Of those, the one with the biggest digit (like −9) is furthest from zero, so it is the smallest. ✓
Watch out. −9 is smaller than −2. The further below zero, the smaller the number.
Key words. The balance is how much money is in a bank account. Overdrawn means the balance is below zero.
Method. A positive balance means the account has money in it. A negative balance means the bank is owed money (overdrawn). Paying in adds money.
- Write the balance as a positive or negative number. Money owed is below zero.Balance now: −£45
- Add £120. Split the move if it crosses zero.−£45 up £120: go up £45 to reach 0, then £75 more → £75
- Write the new balance. If it is negative, the account is overdrawn.£75
Check. Do the opposite: £75 − £120 = −£45. ✓
Watch out. Being −£40 means you owe £40. Paying in £40 only gets you back to £0.
Method. Draw a number line, start at −120 and jump up 45. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go up 45. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.−120 up 45: start below zero and go up 45 → −75
- Write the answer. This is the new depth.−75 m
Check. Do the opposite: −75 − 45 = −120. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−18 up to 0 is 18.
0 up to 35 is 35.
18 + 35 = 53 - Write the answer. 53 m
Check. Start at −18 and go up 53: −18 + 53 = 35. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Watch out
A negative number with a bigger digit is a smaller number: −20 is less than −5, because it is further below zero. And do not just subtract the digits when a number is negative. The gap between −4 and 5 is 9, not 1. Always go through zero.Exercise 1D Negative numbers
Non-calculatorMethod. Find the lowest temperature. The coldest place has the least number.
- Read each temperature. Look at the top of the red liquid on each thermometer.Edinburgh −3°C, Cardiff 2°C, Reykjavik −11°C, Madrid 9°C
- Put them in order, coldest first. Use a number line: further left means colder. Numbers with a minus sign are colder than numbers without one.Reykjavik (−11°C), Edinburgh (−3°C), Cardiff (2°C), Madrid (9°C)
- Write the answer. Reykjavik
Check. Reykjavik at −11°C is below all the others. ✓
Watch out. A bigger number after a minus sign means colder. −11 is colder than −3.
Method. Find the highest temperature. The warmest place has the greatest number.
- Read each temperature. Look at the top of the red liquid on each thermometer.Edinburgh −3°C, Cardiff 2°C, Reykjavik −11°C, Madrid 9°C
- Put them in order, warmest first. Use a number line: further left means colder. Numbers with a minus sign are colder than numbers without one.Madrid (9°C), Cardiff (2°C), Edinburgh (−3°C), Reykjavik (−11°C)
- Write the answer. Madrid
Check. Madrid at 9°C is above all the others. ✓
Watch out. A bigger number after a minus sign means colder. −11 is colder than −3.
Method. The difference between two numbers is how far apart they are on a number line.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−3 up to 0 is 3.
0 up to 2 is 2.
3 + 2 = 5 - Write the answer. 5°C
Check. Start at −3 and go up 5: −3 + 5 = 2. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−11 up to 0 is 11.
0 up to 9 is 9.
11 + 9 = 20 - Write the answer. 20°C
Check. Start at −11 and go up 20: −11 + 20 = 9. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. Coldest first means the smallest temperature first. Put the temperatures in order, then write the city names.
- Read the temperatures. These came from the thermometers.Edinburgh −3°C, Cardiff 2°C, Reykjavik −11°C, Madrid 9°C
- Put the temperatures in order, smallest first. On a number line, left is smaller. Negative numbers come first, and the one with the biggest digit is the smallest.−11, −3, 2, 9
- Write the cities in that order. Reykjavik, Edinburgh, Cardiff, Madrid
Check. The first city is the coldest (Reykjavik) and the last is the warmest (Madrid). ✓
Watch out. −3 is warmer than −11, even though 3 is less than 11.
Method. Find the numbered mark nearest the top of the red liquid, then count the small marks to the top.
- Look at the numbers on the scale. The scale is numbered every 5 degrees. The small marks are 1 degree each.Big numbers: ..., −5, 0, 5, 10, ...
- Find the numbered mark just below the top of the red. The top of the red is between −10 and −5.The mark below is −10.
- Count the small marks above it. Each small mark is 1 degree.2 small marks above −10: −10 + 2 = −8
Check. Count from 0 instead: the top of the red is 8 small marks below 0, so the temperature is −8°C. ✓
Watch out. Going up the scale the numbers get bigger. Below zero, the number nearest the bottom is the smallest.
Method. Work out what each small step is worth. Then count from a number you can read.
- Work out what each step is worth. Two labelled numbers are 20 apart and there are 2 steps between them.20 ÷ 2 = 10
- Work out each missing number. Start at the nearest labelled number. Counting up makes the number bigger. Counting down makes it smaller. Remember that the numbers go up as you go right, even past zero.−30: start at −40 and count 1 step up → −30
−10: start at −20 and count 1 step up → −10
10: start at 0 and count 1 step up → 10
30: start at 20 and count 1 step up → 30 - Write the numbers from left to right. −30, −10, 10, 30
Check. The numbers should go up by 10 each time all the way along, even through 0. ✓
Watch out. Left of zero, numbers get smaller as you go left. Do not count the wrong way!
Key words. A negative number is less than zero. It has a minus sign in front, like −4.
Method. Counting back in 3s means taking away 3 each time. A number line helps when we go through zero.
- Draw a number line. Numbers to the left of 0 are negative (below zero). Numbers to the right are positive.
- Jump back 3 each time, starting from 10. When a jump goes past zero, split it into the part that reaches zero and the part that goes beyond.10 − 3 = 7
7 − 3 = 4
4 − 3 = 1
1 down 3: go down 1 to reach 0, then 2 more below zero → −2
−2 down 3: start at or below zero and go down 3 more → −5 - Write the numbers in order. 7, 4, 1, −2, −5
Check. Go the other way from the last number: −5 + 3 = −2. ✓
Watch out. After 0 comes −1, not 1. Below zero the numbers count down: −1, −2, −3…
Key words. A negative number is less than zero. It has a minus sign in front, like −4.
Method. Counting on in 5s means adding 5 each time. A number line helps when we go through zero.
- Draw a number line. Numbers to the left of 0 are negative (below zero). Numbers to the right are positive.
- Jump on 5 each time, starting from −22. When a jump goes past zero, split it into the part that reaches zero and the part that goes beyond.−22 up 5: start below zero and go up 5 → −17
−17 up 5: start below zero and go up 5 → −12
−12 up 5: start below zero and go up 5 → −7
−7 up 5: start below zero and go up 5 → −2
−2 up 5: go up 2 to reach 0, then 3 more → 3 - Write the numbers in order. −17, −12, −7, −2, 3
Check. Go the other way from the last number: 3 − 5 = −2. ✓
Watch out. After 0 comes −1, not 1. Below zero the numbers count down: −1, −2, −3…
Key words. A negative number is less than zero. It has a minus sign in front, like −4.
Method. Counting back in 10s means taking away 10 each time. A number line helps when we go through zero.
- Draw a number line. Numbers to the left of 0 are negative (below zero). Numbers to the right are positive.
- Jump back 10 each time, starting from 25. When a jump goes past zero, split it into the part that reaches zero and the part that goes beyond.25 − 10 = 15
15 − 10 = 5
5 down 10: go down 5 to reach 0, then 5 more below zero → −5
−5 down 10: start at or below zero and go down 10 more → −15
−15 down 10: start at or below zero and go down 10 more → −25 - Write the numbers in order. 15, 5, −5, −15, −25
Check. Go the other way from the last number: −25 + 10 = −15. ✓
Watch out. After 0 comes −1, not 1. Below zero the numbers count down: −1, −2, −3…
Key words. A negative number is less than zero. It has a minus sign in front, like −4.
Method. Counting on in 4s means adding 4 each time. A number line helps when we go through zero.
- Draw a number line. Numbers to the left of 0 are negative (below zero). Numbers to the right are positive.
- Jump on 4 each time, starting from −18. When a jump goes past zero, split it into the part that reaches zero and the part that goes beyond.−18 up 4: start below zero and go up 4 → −14
−14 up 4: start below zero and go up 4 → −10
−10 up 4: start below zero and go up 4 → −6
−6 up 4: start below zero and go up 4 → −2
−2 up 4: go up 2 to reach 0, then 2 more → 2 - Write the numbers in order. −14, −10, −6, −2, 2
Check. Go the other way from the last number: 2 − 4 = −2. ✓
Watch out. After 0 comes −1, not 1. Below zero the numbers count down: −1, −2, −3…
Method. Put both numbers on a number line. The number further to the right is greater.
- Mark both numbers on a number line. Negative numbers go to the left of zero.
- Find which is further to the right. Further right means bigger.2 is to the right of −3.
- Write the symbol. −3 < 2
Check. In temperatures, −3°C is colder than 2°C. ✓
Watch out. A negative number with a big digit is a small number. −10 is less than −2.
Method. Put both numbers on a number line. The number further to the right is greater.
- Mark both numbers on a number line. Negative numbers go to the left of zero.
- Find which is further to the right. Further right means bigger.−7 is to the right of −17.
- Write the symbol. −17 < −7
Check. In temperatures, −17°C is colder than −7°C. ✓
Watch out. A negative number with a big digit is a small number. −10 is less than −2.
Method. Put both numbers on a number line. The number further to the right is greater.
- Mark both numbers on a number line. Negative numbers go to the left of zero.
- Find which is further to the right. Further right means bigger.0 is to the right of −1.
- Write the symbol. 0 > −1
Check. In temperatures, −1°C is colder than 0°C. ✓
Watch out. A negative number with a big digit is a small number. −10 is less than −2.
Method. Put both numbers on a number line. The number further to the right is greater.
- Mark both numbers on a number line. Negative numbers go to the left of zero.
- Find which is further to the right. Further right means bigger.−25 is to the right of −52.
- Write the symbol. −25 > −52
Check. In temperatures, −52°C is colder than −25°C. ✓
Watch out. A negative number with a big digit is a small number. −10 is less than −2.
Method. Put both numbers on a number line. The number further to the right is greater.
- Mark both numbers on a number line. Negative numbers go to the left of zero.
- Find which is further to the right. Further right means bigger.10 is to the right of −100.
- Write the symbol. −100 < 10
Check. In temperatures, −100°C is colder than 10°C. ✓
Watch out. A negative number with a big digit is a small number. −10 is less than −2.
Method. Put both numbers on a number line. The number further to the right is greater.
- Mark both numbers on a number line. Negative numbers go to the left of zero.
- Find which is further to the right. Further right means bigger.−6 is to the right of −60.
- Write the symbol. −6 > −60
Check. In temperatures, −60°C is colder than −6°C. ✓
Watch out. A negative number with a big digit is a small number. −10 is less than −2.
Method. On a number line, numbers further to the left are smaller. Mark each number, then read them off from left to right.
- Put the numbers on a number line. The line shows which are below zero.
- Read from left to right. Left is smallest, right is biggest.−20, −14, −2, 0, 6, 9
- Write them smallest first. Check you have used every number once.−20, −14, −2, 0, 6, 9
Check. The numbers below zero are the smallest. Of those, the one with the biggest digit (like −9) is furthest from zero, so it is the smallest. ✓
Watch out. −9 is smaller than −2. The further below zero, the smaller the number.
Method. On a number line, numbers further to the left are smaller. Mark each number, then read them off from left to right.
- Put the numbers on a number line. The line shows which are below zero.
- Read from left to right. Left is smallest, right is biggest.−53, −35, −3, 5, 35
- Write them biggest first. Check you have used every number once.35, 5, −3, −35, −53
Check. The numbers below zero are the smallest. Of those, the one with the biggest digit (like −9) is furthest from zero, so it is the smallest. ✓
Watch out. −9 is smaller than −2. The further below zero, the smaller the number.
Method. Draw a number line, start at 6 and jump down 11. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 11. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.6 down 11: go down 6 to reach 0, then 5 more below zero → −5
- Write the answer. This is the new temperature.−5°C
Check. Do the opposite: −5 + 11 = 6. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. Draw a number line, start at −3 and jump up 9. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go up 9. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.−3 up 9: go up 3 to reach 0, then 6 more → 6
- Write the answer. This is the new temperature.6°C
Check. Do the opposite: 6 − 9 = −3. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. Draw a number line, start at −12 and jump up 5. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go up 5. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.−12 up 5: start below zero and go up 5 → −7
- Write the answer. This is the new temperature.−7°C
Check. Do the opposite: −7 − 5 = −12. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. Draw a number line, start at 4 and jump down 15. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 15. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.4 down 15: go down 4 to reach 0, then 11 more below zero → −11
- Write the answer. This is the new temperature.−11°C
Check. Do the opposite: −11 + 15 = 4. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−4 up to 0 is 4.
0 up to 9 is 9.
4 + 9 = 13 - Write the answer. 13°C
Check. Start at −4 and go up 13: −4 + 13 = 9. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. Both numbers are below zero. Find how far each is from zero, then take the smaller from the bigger.−13 is 13 below zero and −2 is 2 below zero.
13 − 2 = 11 - Write the answer. 11°C
Check. Start at −13 and go up 11: −13 + 11 = −2. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−21 up to 0 is 21.
0 up to 6 is 6.
21 + 6 = 27 - Write the answer. 27°C
Check. Start at −21 and go up 27: −21 + 27 = 6. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−17 up to 0 is 17.
0 up to 5 is 5.
17 + 5 = 22 - Write the answer. 22°C
Check. Start at −17 and go up 22: −17 + 22 = 5. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. Both numbers are below zero. Find how far each is from zero, then take the smaller from the bigger.−30 is 30 below zero and −5 is 5 below zero.
30 − 5 = 25 - Write the answer. 25°C
Check. Start at −30 and go up 25: −30 + 25 = −5. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
| What happened | Money in | Money out | Balance |
|---|---|---|---|
| Opening balance | −£30 | ||
| Birthday money paid in | £85 | £55 | |
| Bought a book | £60 | −£5 | |
| Pocket money paid in | £20 | ? | |
| Bought a game | £45 | ? |
Key words. The balance is how much money is in a bank account. Overdrawn means the balance is below zero.
Method. A positive balance means the account has money in it. A negative balance means the bank is owed money (overdrawn). Paying in adds money.
- Write the balance as a positive or negative number. Money owed is below zero.Balance now: −£5
- Add £20. Split the move if it crosses zero.−£5 up £20: go up £5 to reach 0, then £15 more → £15
- Write the new balance. If it is negative, the account is overdrawn.£15
Check. Do the opposite: £15 − £20 = −£5. ✓
Watch out. Being −£40 means you owe £40. Paying in £40 only gets you back to £0.
Key words. The balance is how much money is in a bank account. Overdrawn means the balance is below zero.
Method. A positive balance means the account has money in it. A negative balance means the bank is owed money (overdrawn). Spending takes money away.
- Write the balance as a positive or negative number. Money owed is below zero.Balance now: £15
- Take away £45. Split the move if it crosses zero.£15 down £45: go down £15 to reach 0, then £30 more below zero → −£30
- Write the new balance. If it is negative, the account is overdrawn.−£30 (overdrawn by £30)
Check. Do the opposite: −£30 + £45 = £15. ✓
Watch out. Being −£40 means you owe £40. Paying in £40 only gets you back to £0.
Method. Her balance is below zero, so she owes money. Find how far it is from zero.
- Write her balance. It is negative, so she is overdrawn.Balance: −£30
- Find the distance to zero. To reach 0 she must pay in the amount she owes.0 − (−£30) = £30
- Write the answer. £30
Check. −£30 + £30 = £0. ✓
Watch out. To get from a negative balance to zero, add the amount owed.
Method. The difference between two numbers is how far apart they are on a number line.
- Count the gap. Both numbers are below zero. Find how far each is from zero, then take the smaller from the bigger.−42 is 42 below zero and 0 is 0 below zero.
42 − 0 = 42 - Write the answer. 42 m
Check. Start at −42 and go up 42: −42 + 42 = 0. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−15 up to 0 is 15.
0 up to 28 is 28.
15 + 28 = 43 - Write the answer. 43 m
Check. Start at −15 and go up 43: −15 + 43 = 28. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. Draw a number line, start at −15 and jump down 12. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 12. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.−15 down 12: start at or below zero and go down 12 more → −27
- Write the answer. This is the new depth.−27 m
Check. Do the opposite: −27 + 12 = −15. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. Draw a number line, start at 5 and jump down 8. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 8. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.5 down 8: go down 5 to reach 0, then 3 more below zero → −3
- Write the answer. This is the new floor.−3
Check. Do the opposite: −3 + 8 = 5. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−2 up to 0 is 2.
0 up to 6 is 6.
2 + 6 = 8 - Write the answer. 8 floors
Check. Start at −2 and go up 8: −2 + 8 = 6. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. Add 3 degrees for each hour until the temperature is greater than 0.
- Start at −18°C. Hour 0.Hour 0: −18°C
- Add 3 each hour. Go up in steps of 3, through zero.Hour 0: −18°C
Hour 1: −15°C
Hour 2: −12°C
Hour 3: −9°C
Hour 4: −6°C
Hour 5: −3°C
Hour 6: 0°C
Hour 7: 3°C - Find the first temperature above 0. Hour 6 is exactly 0, which is not above 0.Hour 7 is the first time it is above 0°C.
7 hours
Check. −18 + 7 × 3 = 3. ✓
Watch out. 0°C is not above 0°C. Wait for a positive number.
Method. Draw a number line, start at −5 and jump up 11. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go up 11. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.−5 up 11: go up 5 to reach 0, then 6 more → 6
- Write the answer. This is the new temperature.6°C
Check. Do the opposite: 6 − 11 = −5. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. Draw a number line, start at 6 and jump down 8. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 8. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.6 down 8: go down 6 to reach 0, then 2 more below zero → −2
- Write the answer. This is the new temperature.−2°C
Check. Do the opposite: −2 + 8 = 6. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. The difference between two numbers is how far apart they are on a number line.
- Mark both numbers on a number line. Seeing the gap helps.
- Count the gap. One number is below zero and one is above. Count up to zero first, then on to the other number.−9 up to 0 is 9.
0 up to 6 is 6.
9 + 6 = 15 - Write the answer. 15°C
Check. Start at −9 and go up 15: −9 + 15 = 6. ✓
Watch out. Do not just subtract the digits when one number is negative. Go through zero: −4 and 5 are 9 apart, not 1.
Method. Find the real difference by going through zero, then see what Aisha did.
- Mark the temperatures on a number line. −6 is below zero and 4 is above zero.
- Count the gap. Up from −6 to 0 is 6. Up from 0 to 4 is 4.6 + 4 = 10
- Say what Aisha did. She worked out 6 − 4 = 2. She ignored the fact that the temperatures are on different sides of zero.The correct answer is 10 degrees.
Check. −6 + 10 = 4. ✓
Watch out. When the numbers are on opposite sides of zero, add the distances.
“If you take a number away from 5, the answer is positive.”
Method. Try taking away different numbers from 5. Look at whether the answer is positive, zero or negative.
- Take away a small number. 5 − 3: the answer is above zero.5 − 3 = 2 (positive)
- Take away 5. You reach zero exactly.5 − 5 = 0 (zero is not positive)
- Take away a big number. You go past zero.5 − 8 = −3 (negative)
- Write the answer. It is positive for some numbers and not for others.Sometimes
Check. It is positive only when the number taken away is less than 5. ✓
Watch out. Zero is neither positive nor negative.
Method. Write each one as a number and see which does not match.
- Write each one as a number. Below zero and minus mean negative. Above zero means positive.−7°C = −7
7°C below zero = −7
minus seven degrees = −7
7°C above zero = +7 - Compare them. Three are −7 and one is +7.−7, −7, −7, 7
- Write the odd one out. 7°C above zero
Check. 7°C above zero is 14 degrees warmer than −7°C. ✓
Watch out. Look at whether each temperature is above or below zero.
Method. The other temperature could be 14 degrees warmer or 14 degrees colder. Work out both.
- Find 14 degrees warmer. Go up 14 from −5, through zero.−5 up 14: go up 5 to reach 0, then 9 more → 9
- Find 14 degrees colder. Go down 14 from −5.−5 down 14: start at or below zero and go down 14 more → −19
- Write both answers. 9°C or −19°C
Check. 9 − (−5) = 14 ✓ and −5 − (−19) = 14 ✓
Watch out. There are two answers because “apart” works in both directions.
Rounding and estimating
Printable: Worksheet (PDF) · Answers (PDF) · Open this lesson on its own page
Sometimes we do not need an exact number. A news report might say “about 350,000 people live in the city” when the real number is 347,862. Changing a number to a nearby, simpler number is called rounding. We can round to the nearest 10, 100, 1,000, 10,000 or 100,000.
Look at 347,862 on a number line. To the nearest 1,000 it is between 347,000 and 348,000. The halfway point is 347,500. 347,862 is past halfway, so we round up to 348,000.
Here is the rule. Look at the digit to the right of the place you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down. All the digits to the right become zeros. When a number is exactly halfway, such as 450,000 to the nearest 100,000, we always round up.
Look out for 9s. When you round up a 9, it becomes 10 and carries. 99,960 to the nearest 100 is 100,000. Which numbers round to a given number? To the nearest 1,000, the numbers from 6,500 to 7,499 all round to 7,000. 6,500 is halfway and rounds up. 7,500 is halfway and rounds up to 8,000, so it is not included.
Estimating. To estimate an answer, round the numbers first and then do the easy calculation. 48,920 + 31,150 to the nearest 10,000 is 50,000 + 30,000 = 80,000. The exact answer will be close to 80,000. An estimate is also a good way to check that an answer is sensible.
Key words. To round a number is to change it to a nearby number that is easier to use. An estimate is a sensible answer that is close to the exact one. ≈ means “is about equal to”.
Key ideas
- Look at the digit just to the right of the place you are rounding to.
- 5 or more: round up. 4 or less: round down. Digits to the right become zeros.
- Halfway always rounds up: 450,000 to the nearest 100,000 is 500,000.
- A 9 can carry: 99,960 to the nearest 100 is 100,000.
- Always round the original number. Do not round twice.
- To estimate, round each number first and then calculate.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10 that 347,862 is between. Rounding to the nearest 10 means choosing the closest multiple of 10.347,860 < 347,862 < 347,870
- Picture it on a number line. The halfway point between 347,860 and 347,870 is 347,865.
- Look at the ones digit (the digit just to the right of the tens digit). This digit tells us if we are past halfway.The ones digit is 2.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.2 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the tens column become zeros.347,862 ≈ 347,860 (to the nearest 10)
Check. Distances: 347,862 − 347,860 = 2 and 347,870 − 347,862 = 8. 347,860 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 73,468 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.73,400 < 73,468 < 73,500
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.73,468 ≈ 73,500 (to the nearest 100)
Check. Distances: 73,468 − 73,400 = 68 and 73,500 − 73,468 = 32. 73,500 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 268,450 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.268,000 < 268,450 < 269,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the thousands column become zeros.268,450 ≈ 268,000 (to the nearest 1,000)
Check. Distances: 268,450 − 268,000 = 450 and 269,000 − 268,450 = 550. 268,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 84,730 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.80,000 < 84,730 < 90,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.84,730 ≈ 80,000 (to the nearest 10,000)
Check. Distances: 84,730 − 80,000 = 4,730 and 90,000 − 84,730 = 5,270. 80,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 286,450 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.200,000 < 286,450 < 300,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 8.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.8 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.286,450 ≈ 300,000 (to the nearest 100,000)
Check. Distances: 286,450 − 200,000 = 86,450 and 300,000 − 286,450 = 13,550. 300,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 99,960 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.99,900 < 99,960 < 100,000
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.99,960 ≈ 100,000 (to the nearest 100)
Check. Distances: 99,960 − 99,900 = 60 and 100,000 − 99,960 = 40. 100,000 is the nearer one. ✓
Watch out. A 9 can carry: when you round up a 9 it becomes 10, so the next digit goes up too.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 450,000 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.400,000 < 450,000 < 500,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.450,000 ≈ 500,000 (to the nearest 100,000)
Check. Distances: 450,000 − 400,000 = 50,000 and 500,000 − 450,000 = 50,000. 500,000 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Round the number five times, one place at a time. Always go back to the original number, not to the number you just rounded.
- Round to the nearest 10. Look at the ones digit, 1. It is 4 or less, so round down.542,981 ≈ 542,980
- Round to the nearest 100. Look at the tens digit, 8. It is 5 or more, so round up.542,981 ≈ 543,000
- Round to the nearest 1,000. Look at the hundreds digit, 9. It is 5 or more, so round up.542,981 ≈ 543,000
- Round to the nearest 10,000. Look at the thousands digit, 2. It is 4 or less, so round down.542,981 ≈ 540,000
- Round to the nearest 100,000. Look at the ten thousands digit, 4. It is 4 or less, so round down.542,981 ≈ 500,000
- Put the answers in a table. Seeing them together shows how the numbers change.
Nearest Digit looked at Rounded 10 1 542,980 100 8 543,000 1,000 9 543,000 10,000 2 540,000 100,000 4 500,000
Check. Each rounded number should be close to 542,981. The bigger the place, the further away it can be. ✓
Watch out. Always round the original number each time. Rounding a rounded number can give the wrong answer.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. The numbers that round to 7,000 are all the numbers that are closer to 7,000 than to any other multiple of 1,000, and also the halfway number below it. Find the halfway points on each side.
- Find the multiples of 1,000 on each side. The numbers either side are one step away.6,000, 7,000, 8,000
- Find the halfway point below. Halfway is half of 1,000 = 500 below 7,000. Halfway rounds up, so this number does round to 7,000.7,000 − 500 = 6,500 (smallest)
- Find the halfway point above. The halfway number above is 7,500, but halfway rounds up, so it goes to 8,000. So the largest is 1 less.7,500 − 1 = 7,499 (largest)
- Show it on a number line. The shaded part is every number that rounds to 7,000. The solid dot is included; the open dot is not.
Check. 6,500 rounds up to 7,000 ✓. 6,499 rounds down to 6,000. 7,499 rounds down to 7,000 ✓. 7,500 rounds up to 8,000.
Watch out. The halfway number at the bottom is included but the halfway number at the top is not, because halfway rounds up.
Key words. An estimate is a sensible answer that is close to the exact one. We find it by rounding first.
Method. Round both numbers to the nearest 10,000, then do the easy calculation.
- Round the first number. Look at the digit just to the right of the ten thousands column.48,920 ≈ 50,000
- Round the second number. Do the same.31,150 ≈ 30,000
- Do the easy calculation. Rounded numbers are quick to add and take away.50,000 + 30,000 = 80,000
Check. The exact answer is 80,070, which is close to 80,000. ✓
Watch out. An estimate is not exact. It tells you roughly how big the answer should be.
Key words. An estimate is a sensible answer that is close to the exact one. We find it by rounding first.
Method. Round both numbers to the nearest 100,000, then do the easy calculation.
- Round the first number. Look at the digit just to the right of the hundred thousands column.612,480 ≈ 600,000
- Round the second number. Do the same.187,350 ≈ 200,000
- Do the easy calculation. Rounded numbers are quick to add and take away.600,000 − 200,000 = 400,000
Check. The exact answer is 425,130, which is close to 400,000. ✓
Watch out. An estimate is not exact. It tells you roughly how big the answer should be.
Watch out
Only look at the digit just to the right. To round 3,459 to the nearest 10, the ones digit is 9, so round up to 3,460. Do not round the 9 up to make the 5 a 6 and then round again to 3,500. And 5 rounds up: 3,465 to the nearest 10 is 3,470.Exercise 1E Rounding and estimating
Non-calculatorKey words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10 that 74 is between. Rounding to the nearest 10 means choosing the closest multiple of 10.70 < 74 < 80
- Look at the ones digit (the digit just to the right of the tens digit). This digit tells us if we are past halfway.The ones digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the tens column become zeros.74 ≈ 70 (to the nearest 10)
Check. Distances: 74 − 70 = 4 and 80 − 74 = 6. 70 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10 that 365 is between. Rounding to the nearest 10 means choosing the closest multiple of 10.360 < 365 < 370
- Look at the ones digit (the digit just to the right of the tens digit). This digit tells us if we are past halfway.The ones digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the tens column become zeros.365 ≈ 370 (to the nearest 10)
Check. Distances: 365 − 360 = 5 and 370 − 365 = 5. 370 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10 that 2,384 is between. Rounding to the nearest 10 means choosing the closest multiple of 10.2,380 < 2,384 < 2,390
- Look at the ones digit (the digit just to the right of the tens digit). This digit tells us if we are past halfway.The ones digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the tens column become zeros.2,384 ≈ 2,380 (to the nearest 10)
Check. Distances: 2,384 − 2,380 = 4 and 2,390 − 2,384 = 6. 2,380 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10 that 15,495 is between. Rounding to the nearest 10 means choosing the closest multiple of 10.15,490 < 15,495 < 15,500
- Look at the ones digit (the digit just to the right of the tens digit). This digit tells us if we are past halfway.The ones digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the tens column become zeros.15,495 ≈ 15,500 (to the nearest 10)
Check. Distances: 15,495 − 15,490 = 5 and 15,500 − 15,495 = 5. 15,500 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10 that 70,001 is between. Rounding to the nearest 10 means choosing the closest multiple of 10.70,000 < 70,001 < 70,010
- Look at the ones digit (the digit just to the right of the tens digit). This digit tells us if we are past halfway.The ones digit is 1.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.1 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the tens column become zeros.70,001 ≈ 70,000 (to the nearest 10)
Check. Distances: 70,001 − 70,000 = 1 and 70,010 − 70,001 = 9. 70,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10 that 428,555 is between. Rounding to the nearest 10 means choosing the closest multiple of 10.428,550 < 428,555 < 428,560
- Look at the ones digit (the digit just to the right of the tens digit). This digit tells us if we are past halfway.The ones digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the tens column become zeros.428,555 ≈ 428,560 (to the nearest 10)
Check. Distances: 428,555 − 428,550 = 5 and 428,560 − 428,555 = 5. 428,560 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 347 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.300 < 347 < 400
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.347 ≈ 300 (to the nearest 100)
Check. Distances: 347 − 300 = 47 and 400 − 347 = 53. 300 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 3,650 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.3,600 < 3,650 < 3,700
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.3,650 ≈ 3,700 (to the nearest 100)
Check. Distances: 3,650 − 3,600 = 50 and 3,700 − 3,650 = 50. 3,700 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 62,238 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.62,200 < 62,238 < 62,300
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 3.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.3 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.62,238 ≈ 62,200 (to the nearest 100)
Check. Distances: 62,238 − 62,200 = 38 and 62,300 − 62,238 = 62. 62,200 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 49,950 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.49,900 < 49,950 < 50,000
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.49,950 ≈ 50,000 (to the nearest 100)
Check. Distances: 49,950 − 49,900 = 50 and 50,000 − 49,950 = 50. 50,000 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 128,449 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.128,400 < 128,449 < 128,500
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.128,449 ≈ 128,400 (to the nearest 100)
Check. Distances: 128,449 − 128,400 = 49 and 128,500 − 128,449 = 51. 128,400 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 999,960 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.999,900 < 999,960 < 1,000,000
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.999,960 ≈ 1,000,000 (to the nearest 100)
Check. Distances: 999,960 − 999,900 = 60 and 1,000,000 − 999,960 = 40. 1,000,000 is the nearer one. ✓
Watch out. A 9 can carry: when you round up a 9 it becomes 10, so the next digit goes up too.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 4,280 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.4,000 < 4,280 < 5,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 2.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.2 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the thousands column become zeros.4,280 ≈ 4,000 (to the nearest 1,000)
Check. Distances: 4,280 − 4,000 = 280 and 5,000 − 4,280 = 720. 4,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 36,500 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.36,000 < 36,500 < 37,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the thousands column become zeros.36,500 ≈ 37,000 (to the nearest 1,000)
Check. Distances: 36,500 − 36,000 = 500 and 37,000 − 36,500 = 500. 37,000 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 79,999 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.79,000 < 79,999 < 80,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 9.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.9 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the thousands column become zeros.79,999 ≈ 80,000 (to the nearest 1,000)
Check. Distances: 79,999 − 79,000 = 999 and 80,000 − 79,999 = 1. 80,000 is the nearer one. ✓
Watch out. A 9 can carry: when you round up a 9 it becomes 10, so the next digit goes up too.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 252,499 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.252,000 < 252,499 < 253,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the thousands column become zeros.252,499 ≈ 252,000 (to the nearest 1,000)
Check. Distances: 252,499 − 252,000 = 499 and 253,000 − 252,499 = 501. 252,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 499,501 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.499,000 < 499,501 < 500,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the thousands column become zeros.499,501 ≈ 500,000 (to the nearest 1,000)
Check. Distances: 499,501 − 499,000 = 501 and 500,000 − 499,501 = 499. 500,000 is the nearer one. ✓
Watch out. A 9 can carry: when you round up a 9 it becomes 10, so the next digit goes up too.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 910,350 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.910,000 < 910,350 < 911,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 3.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.3 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the thousands column become zeros.910,350 ≈ 910,000 (to the nearest 1,000)
Check. Distances: 910,350 − 910,000 = 350 and 911,000 − 910,350 = 650. 910,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 38,200 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.30,000 < 38,200 < 40,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 8.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.8 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.38,200 ≈ 40,000 (to the nearest 10,000)
Check. Distances: 38,200 − 30,000 = 8,200 and 40,000 − 38,200 = 1,800. 40,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 65,000 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.60,000 < 65,000 < 70,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.65,000 ≈ 70,000 (to the nearest 10,000)
Check. Distances: 65,000 − 60,000 = 5,000 and 70,000 − 65,000 = 5,000. 70,000 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 124,999 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.120,000 < 124,999 < 130,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.124,999 ≈ 120,000 (to the nearest 10,000)
Check. Distances: 124,999 − 120,000 = 4,999 and 130,000 − 124,999 = 5,001. 120,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 449,500 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.440,000 < 449,500 < 450,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 9.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.9 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.449,500 ≈ 450,000 (to the nearest 10,000)
Check. Distances: 449,500 − 440,000 = 9,500 and 450,000 − 449,500 = 500. 450,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 895,001 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.890,000 < 895,001 < 900,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.895,001 ≈ 900,000 (to the nearest 10,000)
Check. Distances: 895,001 − 890,000 = 5,001 and 900,000 − 895,001 = 4,999. 900,000 is the nearer one. ✓
Watch out. A 9 can carry: when you round up a 9 it becomes 10, so the next digit goes up too.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 7,300 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.0 < 7,300 < 10,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 7.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.7 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.7,300 ≈ 10,000 (to the nearest 10,000)
Check. Distances: 7,300 − 0 = 7,300 and 10,000 − 7,300 = 2,700. 10,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 340,000 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.300,000 < 340,000 < 400,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.340,000 ≈ 300,000 (to the nearest 100,000)
Check. Distances: 340,000 − 300,000 = 40,000 and 400,000 − 340,000 = 60,000. 300,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 450,000 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.400,000 < 450,000 < 500,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.450,000 ≈ 500,000 (to the nearest 100,000)
Check. Distances: 450,000 − 400,000 = 50,000 and 500,000 − 450,000 = 50,000. 500,000 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 249,999 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.200,000 < 249,999 < 300,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.249,999 ≈ 200,000 (to the nearest 100,000)
Check. Distances: 249,999 − 200,000 = 49,999 and 300,000 − 249,999 = 50,001. 200,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 650,100 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.600,000 < 650,100 < 700,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.650,100 ≈ 700,000 (to the nearest 100,000)
Check. Distances: 650,100 − 600,000 = 50,100 and 700,000 − 650,100 = 49,900. 700,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 85,000 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.0 < 85,000 < 100,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 8.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.8 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.85,000 ≈ 100,000 (to the nearest 100,000)
Check. Distances: 85,000 − 0 = 85,000 and 100,000 − 85,000 = 15,000. 100,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 960,500 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.900,000 < 960,500 < 1,000,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.960,500 ≈ 1,000,000 (to the nearest 100,000)
Check. Distances: 960,500 − 900,000 = 60,500 and 1,000,000 − 960,500 = 39,500. 1,000,000 is the nearer one. ✓
Watch out. A 9 can carry: when you round up a 9 it becomes 10, so the next digit goes up too.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10 that 354,628 is between. Rounding to the nearest 10 means choosing the closest multiple of 10.354,620 < 354,628 < 354,630
- Look at the ones digit (the digit just to the right of the tens digit). This digit tells us if we are past halfway.The ones digit is 8.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.8 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the tens column become zeros.354,628 ≈ 354,630 (to the nearest 10)
Check. Distances: 354,628 − 354,620 = 8 and 354,630 − 354,628 = 2. 354,630 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 354,628 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.354,600 < 354,628 < 354,700
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 2.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.2 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.354,628 ≈ 354,600 (to the nearest 100)
Check. Distances: 354,628 − 354,600 = 28 and 354,700 − 354,628 = 72. 354,600 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 354,628 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.354,000 < 354,628 < 355,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the thousands column become zeros.354,628 ≈ 355,000 (to the nearest 1,000)
Check. Distances: 354,628 − 354,000 = 628 and 355,000 − 354,628 = 372. 355,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 354,628 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.350,000 < 354,628 < 360,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.354,628 ≈ 350,000 (to the nearest 10,000)
Check. Distances: 354,628 − 350,000 = 4,628 and 360,000 − 354,628 = 5,372. 350,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100,000 that 354,628 is between. Rounding to the nearest 100,000 means choosing the closest multiple of 100,000.300,000 < 354,628 < 400,000
- Look at the ten thousands digit (the digit just to the right of the hundred thousands digit). This digit tells us if we are past halfway.The ten thousands digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundred thousands column become zeros.354,628 ≈ 400,000 (to the nearest 100,000)
Check. Distances: 354,628 − 300,000 = 54,628 and 400,000 − 354,628 = 45,372. 400,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 72,640 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.72,000 < 72,640 < 73,000
- Picture it on a number line. The halfway point between 72,000 and 73,000 is 72,500.
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the thousands column become zeros.72,640 ≈ 73,000 (to the nearest 1,000)
Check. Distances: 72,640 − 72,000 = 640 and 73,000 − 72,640 = 360. 73,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Method. First read the number the arrow points to. Then round it.
- Work out what each small mark is worth. The line goes from 40,000 to 50,000 in 10 equal gaps.50,000 − 40,000 = 10,000 and 10,000 ÷ 10 = 1,000
- Read the arrow. It is 6 marks after 40,000.40,000 + 6 × 1,000 = 46,000
- Round 46,000 to the nearest 10,000. Look at the thousands digit: 6 is 5 or more, so round up.46,000 ≈ 50,000
Check. 46,000 is 4,000 from 50,000. The other choice is 6,000 away. ✓
Watch out. Read the arrow first, then round. Do not just pick the nearest label.
| Town | People |
|---|---|
| Fenby | 43,816 |
| Grimsworth | 128,450 |
| Hale | 96,500 |
| Ingleby | 252,049 |
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 43,816 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.40,000 < 43,816 < 50,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 3.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.3 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.43,816 ≈ 40,000 (to the nearest 10,000)
Check. Distances: 43,816 − 40,000 = 3,816 and 50,000 − 43,816 = 6,184. 40,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 128,450 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.120,000 < 128,450 < 130,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 8.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.8 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.128,450 ≈ 130,000 (to the nearest 10,000)
Check. Distances: 128,450 − 120,000 = 8,450 and 130,000 − 128,450 = 1,550. 130,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 96,500 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.90,000 < 96,500 < 100,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.96,500 ≈ 100,000 (to the nearest 10,000)
Check. Distances: 96,500 − 90,000 = 6,500 and 100,000 − 96,500 = 3,500. 100,000 is the nearer one. ✓
Watch out. A 9 can carry: when you round up a 9 it becomes 10, so the next digit goes up too.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 252,049 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.250,000 < 252,049 < 260,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 2.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.2 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.252,049 ≈ 250,000 (to the nearest 10,000)
Check. Distances: 252,049 − 250,000 = 2,049 and 260,000 − 252,049 = 7,951. 250,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Method. Round each number to the nearest 10,000 by looking at the thousands digit.
- Round each number. 5 or more rounds up. 4 or less rounds down.55,000: thousands digit 5 → 60,000
64,999: thousands digit 4 → 60,000
65,000: thousands digit 5 → 70,000
59,500: thousands digit 9 → 60,000 - Find the one that is not 60,000. 65,000 rounds to 70,000.
- Write the answer. 65,000
Check. 65,000 is exactly halfway between 60,000 and 70,000, and halfway rounds up. ✓
Watch out. Numbers exactly halfway round up.
Method. The thousands digit decides if we round up or down to the nearest 10,000. Try each digit.
- Look at what 70,000 needs. The number 6?,500 is between 60,000 and 70,000. To round up to 70,000 it must be at least halfway, which is 65,000.Halfway = (60,000 + 70,000) ÷ 2 = 65,000
- Try each thousands digit. A thousands digit of 5 or more rounds up.60,500: thousands digit 0 → round down to 60,000
61,500: thousands digit 1 → round down to 60,000
62,500: thousands digit 2 → round down to 60,000
63,500: thousands digit 3 → round down to 60,000
64,500: thousands digit 4 → round down to 60,000
65,500: thousands digit 5 → round up to 70,000
66,500: thousands digit 6 → round up to 70,000
67,500: thousands digit 7 → round up to 70,000
68,500: thousands digit 8 → round up to 70,000
69,500: thousands digit 9 → round up to 70,000 - Write the digits that work. 5, 6, 7, 8 or 9
Check. 65,500 > 65,000, so it rounds up. 64,500 < 65,000, so it rounds down. ✓
Watch out. Only the thousands digit matters here. The hundreds digit 5 does not change the answer.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. The numbers that round to 250 are all the numbers that are closer to 250 than to any other multiple of 10, and also the halfway number below it. Find the halfway points on each side.
- Find the multiples of 10 on each side. The numbers either side are one step away.240, 250, 260
- Find the halfway point below. Halfway is half of 10 = 5 below 250. Halfway rounds up, so this number does round to 250.250 − 5 = 245 (smallest)
- Find the halfway point above. The halfway number above is 255, but halfway rounds up, so it goes to 260. So the largest is 1 less.255 − 1 = 254 (largest)
- Show it on a number line. The shaded part is every number that rounds to 250. The solid dot is included; the open dot is not.
Check. 245 rounds up to 250 ✓. 244 rounds down to 240. 254 rounds down to 250 ✓. 255 rounds up to 260.
Watch out. The halfway number at the bottom is included but the halfway number at the top is not, because halfway rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. The numbers that round to 7,000 are all the numbers that are closer to 7,000 than to any other multiple of 1,000, and also the halfway number below it. Find the halfway points on each side.
- Find the multiples of 1,000 on each side. The numbers either side are one step away.6,000, 7,000, 8,000
- Find the halfway point below. Halfway is half of 1,000 = 500 below 7,000. Halfway rounds up, so this number does round to 7,000.7,000 − 500 = 6,500 (smallest)
- Find the halfway point above. The halfway number above is 7,500, but halfway rounds up, so it goes to 8,000. So the largest is 1 less.7,500 − 1 = 7,499 (largest)
- Show it on a number line. The shaded part is every number that rounds to 7,000. The solid dot is included; the open dot is not.
Check. 6,500 rounds up to 7,000 ✓. 6,499 rounds down to 6,000. 7,499 rounds down to 7,000 ✓. 7,500 rounds up to 8,000.
Watch out. The halfway number at the bottom is included but the halfway number at the top is not, because halfway rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. The numbers that round to 300,000 are all the numbers that are closer to 300,000 than to any other multiple of 100,000, and also the halfway number below it. Find the halfway points on each side.
- Find the multiples of 100,000 on each side. The numbers either side are one step away.200,000, 300,000, 400,000
- Find the halfway point below. Halfway is half of 100,000 = 50,000 below 300,000. Halfway rounds up, so this number does round to 300,000.300,000 − 50,000 = 250,000 (smallest)
- Find the halfway point above. The halfway number above is 350,000, but halfway rounds up, so it goes to 400,000. So the largest is 1 less.350,000 − 1 = 349,999 (largest)
- Show it on a number line. The shaded part is every number that rounds to 300,000. The solid dot is included; the open dot is not.
Check. 250,000 rounds up to 300,000 ✓. 249,999 rounds down to 200,000. 349,999 rounds down to 300,000 ✓. 350,000 rounds up to 400,000.
Watch out. The halfway number at the bottom is included but the halfway number at the top is not, because halfway rounds up.
Key words. An estimate is a sensible answer that is close to the exact one. We find it by rounding first.
Method. Round both numbers to the nearest 1,000, then do the easy calculation.
- Round the first number. Look at the digit just to the right of the thousands column.6,214 ≈ 6,000
- Round the second number. Do the same.2,788 ≈ 3,000
- Do the easy calculation. Rounded numbers are quick to add and take away.6,000 + 3,000 = 9,000
Check. The exact answer is 9,002, which is close to 9,000. ✓
Watch out. An estimate is not exact. It tells you roughly how big the answer should be.
Key words. An estimate is a sensible answer that is close to the exact one. We find it by rounding first.
Method. Round both numbers to the nearest 10,000, then do the easy calculation.
- Round the first number. Look at the digit just to the right of the ten thousands column.48,920 ≈ 50,000
- Round the second number. Do the same.21,350 ≈ 20,000
- Do the easy calculation. Rounded numbers are quick to add and take away.50,000 − 20,000 = 30,000
Check. The exact answer is 27,570, which is close to 30,000. ✓
Watch out. An estimate is not exact. It tells you roughly how big the answer should be.
Key words. An estimate is a sensible answer that is close to the exact one. We find it by rounding first.
Method. Round both numbers to the nearest 100,000, then do the easy calculation.
- Round the first number. Look at the digit just to the right of the hundred thousands column.418,200 ≈ 400,000
- Round the second number. Do the same.189,700 ≈ 200,000
- Do the easy calculation. Rounded numbers are quick to add and take away.400,000 + 200,000 = 600,000
Check. The exact answer is 607,900, which is close to 600,000. ✓
Watch out. An estimate is not exact. It tells you roughly how big the answer should be.
Method. Round both numbers to the nearest 10,000 and add. Compare the estimate with Amira’s answer. Then add the exact numbers.
- Estimate. Round each number to the nearest 10,000.38,420 ≈ 40,000 and 41,690 ≈ 40,000
40,000 + 40,000 = 80,000 - Compare with Amira’s answer. The exact answer should be close to the estimate.70,110 is 10,000 less than 80,000. That is too far away, so she has made a mistake.
- Work out the exact answer. Add column by column.38,420 + 41,690 = 80,110
Check. 80,110 is close to the estimate of 80,000. ✓
Watch out. Amira forgot to carry 1 in the thousands column. An estimate catches mistakes like this.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. The numbers that round to 42,000 are all the numbers that are closer to 42,000 than to any other multiple of 1,000, and also the halfway number below it. Find the halfway points on each side.
- Find the multiples of 1,000 on each side. The numbers either side are one step away.41,000, 42,000, 43,000
- Find the halfway point below. Halfway is half of 1,000 = 500 below 42,000. Halfway rounds up, so this number does round to 42,000.42,000 − 500 = 41,500 (smallest)
- Find the halfway point above. The halfway number above is 42,500, but halfway rounds up, so it goes to 43,000. So the largest is 1 less.42,500 − 1 = 42,499 (largest)
- Show it on a number line. The shaded part is every number that rounds to 42,000. The solid dot is included; the open dot is not.
Check. 41,500 rounds up to 42,000 ✓. 41,499 rounds down to 41,000. 42,499 rounds down to 42,000 ✓. 42,500 rounds up to 43,000.
Watch out. The halfway number at the bottom is included but the halfway number at the top is not, because halfway rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 1,000 that 14,950 is between. Rounding to the nearest 1,000 means choosing the closest multiple of 1,000.14,000 < 14,950 < 15,000
- Look at the hundreds digit (the digit just to the right of the thousands digit). This digit tells us if we are past halfway.The hundreds digit is 9.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.9 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the thousands column become zeros.14,950 ≈ 15,000 (to the nearest 1,000)
Check. Distances: 14,950 − 14,000 = 950 and 15,000 − 14,950 = 50. 15,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 14,950 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.14,900 < 14,950 < 15,000
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.14,950 ≈ 15,000 (to the nearest 100)
Check. Distances: 14,950 − 14,900 = 50 and 15,000 − 14,950 = 50. 15,000 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 14,950 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.10,000 < 14,950 < 20,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 4.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.4 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.14,950 ≈ 10,000 (to the nearest 10,000)
Check. Distances: 14,950 − 10,000 = 4,950 and 20,000 − 14,950 = 5,050. 10,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Method. Round 349,500 to the nearest 100,000 in one go, by looking at the ten thousands digit. Then compare with Leo.
- Find the hundred thousands either side. 349,500 is between 300,000 and 400,000.300,000 < 349,500 < 400,000
- Look at the ten thousands digit. It is 4, which is 4 or less, so round down.349,500 ≈ 300,000
- Say what Leo did. Leo rounded twice: first to 350,000, then again. This is wrong, because we must always round the original number.No. The correct answer is 300,000.
Check. 349,500 is 49,500 from 300,000 but 50,500 from 400,000. 300,000 is nearer. ✓
Watch out. Never round a rounded number. Go back to the original each time.
“A number rounded to the nearest 10 is the same as when it is rounded to the nearest 100.”
Method. Try some numbers and round them both ways.
- Try 304. Nearest 10 and nearest 100.304 ≈ 300 (nearest 10) and 304 ≈ 300 (nearest 100). Same. It works.
- Try 356. Nearest 10 and nearest 100.356 ≈ 360 (nearest 10) but 356 ≈ 400 (nearest 100). Different. It does not work.
- Write the answer. It works for some numbers and not others.Sometimes
Check. It only works when the tens digit and ones digit round the same way, for example numbers that end in 0 to 4 with a tens digit of 0 to 4. ✓
Watch out. One example that works does not prove “always”.
Method. Find how far 250,000 is from each number.
- Distance from 200,000. Subtract.250,000 − 200,000 = 50,000
- Distance from 300,000. Subtract.300,000 − 250,000 = 50,000
- Decide. It is exactly halfway. We have a rule for halfway: always round up.250,000 ≈ 300,000. Zainab is not right.
Check. Halfway between 200,000 and 300,000 is (200,000 + 300,000) ÷ 2 = 250,000. ✓
Watch out. Halfway is not closer to either side. We round up so that everyone gets the same answer.
Roman numerals to 1,000 and years
Printable: Worksheet (PDF) · Answers (PDF) · Open this lesson on its own page
In Year 4 you learned the Roman symbols I, V, X, L and C. To read numbers up to 1,000 you need two more: D = 500 and M = 1,000.
The rules. (1) Same symbols add up: XXX = 30. (2) A smaller symbol after a bigger one is added: DC = 500 + 100 = 600. (3) A smaller symbol before a bigger one is taken away: CM = 1,000 − 100 = 900. (4) Only I, X and C can be taken away, and only from the next two bigger symbols: I before V or X, X before L or C, C before D or M. (5) Never write the same symbol more than three times in a row. To write a number, do the thousands first, then the hundreds, then the tens, then the ones.
| Ones | Roman | Tens | Roman | Hundreds | Roman |
|---|---|---|---|---|---|
| 1 | I | 10 | X | 100 | C |
| 2 | II | 20 | XX | 200 | CC |
| 3 | III | 30 | XXX | 300 | CCC |
| 4 | IV | 40 | XL | 400 | CD |
| 5 | V | 50 | L | 500 | D |
| 6 | VI | 60 | LX | 600 | DC |
| 7 | VII | 70 | LXX | 700 | DCC |
| 8 | VIII | 80 | LXXX | 800 | DCCC |
| 9 | IX | 90 | XC | 900 | CM |
Years. Roman numerals are still used for years on buildings, films and TV programmes. The year 1999 is M + CM + XC + IX = MCMXCIX. The year 2026 is MM + XX + VI = MMXXVI. The Romans had no symbol for zero, so a zero in a number is simply left out: 2,006 has no tens or hundreds, so it is MMVI.
Key words. A numeral is a symbol for a number. Roman numerals use the letters I, V, X, L, C, D and M.
Key ideas
- I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000.
- Smaller after bigger: add. Smaller before bigger: take away (IV, IX, XL, XC, CD, CM).
- Never more than three of the same symbol in a row.
- Write thousands, then hundreds, then tens, then ones: 1,994 = M + CM + XC + IV = MCMXCIV.
- A zero is left out. There is no Roman symbol for zero.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.CD = 500 − 100 = 400 (small symbol in front, so take it away)
XL = 50 − 10 = 40 (small symbol in front, so take it away)
V = 5
I = 1
I = 1 - Add the values. Add the biggest groups first.400 + 40 + 5 + 1 + 1 = 447
- Write the answer. 447
Check. Write 447 in Roman numerals: CD + XL + VII = CDXLVII. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
M = 1,000
X = 10
X = 10
V = 5
I = 1 - Add the values. Add the biggest groups first.1,000 + 1,000 + 10 + 10 + 5 + 1 = 2,026
- Write the answer. 2026
Check. Write 2,026 in Roman numerals: MM + XX + VI = MMXXVI. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.649 = 600 + 40 + 9
- Write 600 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).600 = DC
- Write 40 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).40 = XL
- Write 9 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).9 = IX
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.DC + XL + IX = DCXLIX
Check. Read it back: 500 + 100 + 40 + 9 = 649. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.1,994 = 1,000 + 900 + 90 + 4
- Write 1,000 in Roman numerals. M is 1,000.1,000 = M
- Write 900 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).900 = CM
- Write 90 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).90 = XC
- Write 4 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).4 = IV
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.M + CM + XC + IV = MCMXCIV
Check. Read it back: 1,000 + 900 + 90 + 4 = 1,994. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.1,066 = 1,000 + 60 + 6
- Write 1,000 in Roman numerals. M is 1,000.1,000 = M
- Write 60 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).60 = LX
- Write 6 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).6 = VI
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.M + LX + VI = MLXVI
Check. Read it back: 1,000 + 50 + 10 + 5 + 1 = 1,066. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
D = 500
C = 100
C = 100
C = 100
XC = 100 − 10 = 90 (small symbol in front, so take it away)
V = 5 - Add the values. Add the biggest groups first.1,000 + 500 + 100 + 100 + 100 + 90 + 5 = 1,895
- Write the answer. 1895
Check. Write 1,895 in Roman numerals: M + DCCC + XC + V = MDCCCXCV. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numerals into numbers, do the calculation, then change the answer back into Roman numerals.
- Change DLXII into a number. Split it into groups and add.DLXII = D (500) + L (50) + X (10) + I (1) + I (1) = 562
- Change CXXXVIII into a number. Do the same.CXXXVIII = C (100) + X (10) + X (10) + X (10) + V (5) + I (1) + I (1) + I (1) = 138
- Do the calculation. Use our normal numbers.562 + 138 = 700
- Change the answer back to Roman numerals. Thousands, hundreds, tens, then ones.700 = DCC = DCC
Check. Read DCC again: 500 + 100 + 100 = 700. ✓
Watch out. Roman numerals are hard to add directly. Change them to numbers first.
Method. Change both Roman numerals into numbers. Then compare the numbers.
- Change CM into a number. Split into groups and add.CM = 900
- Change DCCLXXXVIII into a number. Do the same.DCCLXXXVIII = 788
- Compare the numbers. Compare from the left, as usual.900 > 788
- Write the answer with the Roman numerals. CM > DCCLXXXVIII
Check. CM is 112 more than DCCLXXXVIII. ✓
Watch out. Do not compare the number of letters. A short numeral like CM (900) can be bigger than a long one like DCCLXXXVIII (788).
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numeral into a year in digits, then take it away from the later year.
- Change MCMLXIX into a year. Split it into groups and add.MCMLXIX = M (1000) + CM (1000 − 100) + L (50) + X (10) + IX (10 − 1) = 1969
- Decide which year is later. The later year is the bigger number. We take the earlier year away from it.1969 < 2026
- Subtract from the later year. 2026 is the later year.2026 − 1969 = 57
Check. 1969 + 57 = 2026. ✓
Watch out. Write the years as ordinary numbers before you subtract.
Watch out
Do not write 49 as IL or 99 as IC. I can only go before V or X, so 49 is XL + IX = XLIX and 99 is XC + IX = XCIX. And do not write 4 as IIII or 900 as DCCCC: they are IV and CM. Never put the same symbol more than three times in a row.Exercise 1F Roman numerals
Non-calculatorKey words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.C = 100
L = 50
IX = 10 − 1 = 9 (small symbol in front, so take it away) - Add the values. Add the biggest groups first.100 + 50 + 9 = 159
- Write the answer. 159
Check. Write 159 in Roman numerals: C + L + IX = CLIX. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.D = 500
XL = 50 − 10 = 40 (small symbol in front, so take it away)
IV = 5 − 1 = 4 (small symbol in front, so take it away) - Add the values. Add the biggest groups first.500 + 40 + 4 = 544
- Write the answer. 544
Check. Write 544 in Roman numerals: D + XL + IV = DXLIV. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.CM = 1000 − 100 = 900 (small symbol in front, so take it away)
XC = 100 − 10 = 90 (small symbol in front, so take it away) - Add the values. Add the biggest groups first.900 + 90 = 990
- Write the answer. 990
Check. Write 990 in Roman numerals: CM + XC = CMXC. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.D = 500
C = 100
C = 100
C = 100
L = 50
X = 10
X = 10
X = 10
V = 5
I = 1
I = 1
I = 1 - Add the values. Add the biggest groups first.500 + 100 + 100 + 100 + 50 + 10 + 10 + 10 + 5 + 1 + 1 + 1 = 888
- Write the answer. 888
Check. Write 888 in Roman numerals: DCCC + LXXX + VIII = DCCCLXXXVIII. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.CD = 500 − 100 = 400 (small symbol in front, so take it away)
XL = 50 − 10 = 40 (small symbol in front, so take it away)
IX = 10 − 1 = 9 (small symbol in front, so take it away) - Add the values. Add the biggest groups first.400 + 40 + 9 = 449
- Write the answer. 449
Check. Write 449 in Roman numerals: CD + XL + IX = CDXLIX. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
CD = 500 − 100 = 400 (small symbol in front, so take it away)
L = 50
X = 10 - Add the values. Add the biggest groups first.1,000 + 400 + 50 + 10 = 1,460
- Write the answer. 1,460
Check. Write 1,460 in Roman numerals: M + CD + LX = MCDLX. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.134 = 100 + 30 + 4
- Write 100 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).100 = C
- Write 30 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).30 = XXX
- Write 4 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).4 = IV
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.C + XXX + IV = CXXXIV
Check. Read it back: 100 + 10 + 10 + 10 + 4 = 134. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.478 = 400 + 70 + 8
- Write 400 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).400 = CD
- Write 70 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).70 = LXX
- Write 8 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).8 = VIII
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.CD + LXX + VIII = CDLXXVIII
Check. Read it back: 400 + 50 + 10 + 10 + 5 + 1 + 1 + 1 = 478. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.909 = 900 + 9
- Write 900 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).900 = CM
- Write 9 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).9 = IX
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.CM + IX = CMIX
Check. Read it back: 900 + 9 = 909. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.640 = 600 + 40
- Write 600 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).600 = DC
- Write 40 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).40 = XL
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.DC + XL = DCXL
Check. Read it back: 500 + 100 + 40 = 640. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.999 = 900 + 90 + 9
- Write 900 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).900 = CM
- Write 90 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).90 = XC
- Write 9 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).9 = IX
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.CM + XC + IX = CMXCIX
Check. Read it back: 900 + 90 + 9 = 999. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.1,000 is just one part
- Write 1,000 in Roman numerals. M is 1,000.1,000 = M
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.M = M
Check. Read it back: 1,000 = 1,000. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.400 is just one part
- Write 400 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).400 = CD
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.CD = CD
Check. Read it back: 400 = 400. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.500 is just one part
- Write 500 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).500 = D
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.D = D
Check. Read it back: 500 = 500. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.900 is just one part
- Write 900 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).900 = CM
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.CM = CM
Check. Read it back: 900 = 900. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.600 is just one part
- Write 600 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).600 = DC
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.DC = DC
Check. Read it back: 500 + 100 = 600. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.90 is just one part
- Write 90 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).90 = XC
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.XC = XC
Check. Read it back: 90 = 90. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.1,000 is just one part
- Write 1,000 in Roman numerals. M is 1,000.1,000 = M
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.M = M
Check. Read it back: 1,000 = 1,000. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
CM = 1000 − 100 = 900 (small symbol in front, so take it away)
L = 50
X = 10
X = 10
X = 10
IV = 5 − 1 = 4 (small symbol in front, so take it away) - Add the values. Add the biggest groups first.1,000 + 900 + 50 + 10 + 10 + 10 + 4 = 1,984
- Write the answer. 1984
Check. Write 1,984 in Roman numerals: M + CM + LXXX + IV = MCMLXXXIV. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
D = 500
C = 100
L = 50
X = 10
V = 5
I = 1 - Add the values. Add the biggest groups first.1,000 + 500 + 100 + 50 + 10 + 5 + 1 = 1,666
- Write the answer. 1666
Check. Write 1,666 in Roman numerals: M + DC + LX + VI = MDCLXVI. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
C = 100
C = 100
X = 10
V = 5 - Add the values. Add the biggest groups first.1,000 + 100 + 100 + 10 + 5 = 1,215
- Write the answer. 1215
Check. Write 1,215 in Roman numerals: M + CC + X + V = MCCXV. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
M = 1,000
X = 10
X = 10
IV = 5 − 1 = 4 (small symbol in front, so take it away) - Add the values. Add the biggest groups first.1,000 + 1,000 + 10 + 10 + 4 = 2,024
- Write the answer. 2024
Check. Write 2,024 in Roman numerals: MM + XX + IV = MMXXIV. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
CM = 1000 − 100 = 900 (small symbol in front, so take it away)
X = 10
I = 1
I = 1 - Add the values. Add the biggest groups first.1,000 + 900 + 10 + 1 + 1 = 1,912
- Write the answer. 1912
Check. Write 1,912 in Roman numerals: M + CM + X + II = MCMXII. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.1,066 = 1,000 + 60 + 6
- Write 1,000 in Roman numerals. M is 1,000.1,000 = M
- Write 60 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).60 = LX
- Write 6 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).6 = VI
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.M + LX + VI = MLXVI
Check. Read it back: 1,000 + 50 + 10 + 5 + 1 = 1,066. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.1,666 = 1,000 + 600 + 60 + 6
- Write 1,000 in Roman numerals. M is 1,000.1,000 = M
- Write 600 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).600 = DC
- Write 60 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).60 = LX
- Write 6 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).6 = VI
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.M + DC + LX + VI = MDCLXVI
Check. Read it back: 1,000 + 500 + 100 + 50 + 10 + 5 + 1 = 1,666. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.1,948 = 1,000 + 900 + 40 + 8
- Write 1,000 in Roman numerals. M is 1,000.1,000 = M
- Write 900 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).900 = CM
- Write 40 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).40 = XL
- Write 8 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).8 = VIII
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.M + CM + XL + VIII = MCMXLVIII
Check. Read it back: 1,000 + 900 + 40 + 5 + 1 + 1 + 1 = 1,948. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.2,026 = 2,000 + 20 + 6
- Write 2,000 in Roman numerals. M is 1,000.2,000 = MM
- Write 20 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).20 = XX
- Write 6 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).6 = VI
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.MM + XX + VI = MMXXVI
Check. Read it back: 1,000 + 1,000 + 10 + 10 + 5 + 1 = 2,026. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Method. Change both Roman numerals into numbers. Then compare the numbers.
- Change CDXL into a number. Split into groups and add.CDXL = 440
- Change CCCXLIV into a number. Do the same.CCCXLIV = 344
- Compare the numbers. Compare from the left, as usual.440 > 344
- Write the answer with the Roman numerals. CDXL > CCCXLIV
Check. CDXL is 96 more than CCCXLIV. ✓
Watch out. Do not compare the number of letters. A short numeral like CM (900) can be bigger than a long one like DCCLXXXVIII (788).
Method. Change both Roman numerals into numbers. Then compare the numbers.
- Change DCCLXXXIX into a number. Split into groups and add.DCCLXXXIX = 789
- Change DCCXC into a number. Do the same.DCCXC = 790
- Compare the numbers. Compare from the left, as usual.789 < 790
- Write the answer with the Roman numerals. DCCLXXXIX < DCCXC
Check. DCCLXXXIX is 1 less than DCCXC. ✓
Watch out. Do not compare the number of letters. A short numeral like CM (900) can be bigger than a long one like DCCLXXXVIII (788).
Method. Change both Roman numerals into numbers. Then compare the numbers.
- Change CM into a number. Split into groups and add.CM = 900
- Change DCCCXCIX into a number. Do the same.DCCCXCIX = 899
- Compare the numbers. Compare from the left, as usual.900 > 899
- Write the answer with the Roman numerals. CM > DCCCXCIX
Check. CM is 1 more than DCCCXCIX. ✓
Watch out. Do not compare the number of letters. A short numeral like CM (900) can be bigger than a long one like DCCLXXXVIII (788).
Method. Change each Roman numeral into a number, order the numbers, then write the Roman numerals in that order.
- Change each to a number. Split into groups and add.DCLXVI = 666
DCXLIX = 649
DLXVI = 566
DCC = 700
CMXC = 990 - Order the numbers. Compare from the left (hundreds first).566, 649, 666, 700, 990
- Write the Roman numerals in that order. DLXVI, DCXLIX, DCLXVI, DCC, CMXC
Check. There are 5 numerals in the question and 5 in the answer. ✓
Watch out. Write the answer in Roman numerals, because that is what the question asks for.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numerals into numbers, do the calculation, then change the answer back into Roman numerals.
- Change XC into a number. Split it into groups and add.XC = XC (100 − 10) = 90
- Change CCX into a number. Do the same.CCX = C (100) + C (100) + X (10) = 210
- Do the calculation. Use our normal numbers.90 + 210 = 300
- Change the answer back to Roman numerals. Thousands, hundreds, tens, then ones.300 = CCC = CCC
Check. Read CCC again: 100 + 100 + 100 = 300. ✓
Watch out. Roman numerals are hard to add directly. Change them to numbers first.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numerals into numbers, do the calculation, then change the answer back into Roman numerals.
- Change DL into a number. Split it into groups and add.DL = D (500) + L (50) = 550
- Change CCCXV into a number. Do the same.CCCXV = C (100) + C (100) + C (100) + X (10) + V (5) = 315
- Do the calculation. Use our normal numbers.550 + 315 = 865
- Change the answer back to Roman numerals. Thousands, hundreds, tens, then ones.865 = DCCC + LX + V = DCCCLXV
Check. Read DCCCLXV again: 500 + 100 + 100 + 100 + 50 + 10 + 5 = 865. ✓
Watch out. Roman numerals are hard to add directly. Change them to numbers first.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numerals into numbers, do the calculation, then change the answer back into Roman numerals.
- Change M into a number. Split it into groups and add.M = M (1000) = 1,000
- Change CDXL into a number. Do the same.CDXL = CD (500 − 100) + XL (50 − 10) = 440
- Do the calculation. Use our normal numbers.1,000 − 440 = 560
- Change the answer back to Roman numerals. Thousands, hundreds, tens, then ones.560 = D + LX = DLX
Check. Read DLX again: 500 + 50 + 10 = 560. ✓
Watch out. Roman numerals are hard to add directly. Change them to numbers first.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numerals into numbers, do the calculation, then change the answer back into Roman numerals.
- Change DCCC into a number. Split it into groups and add.DCCC = D (500) + C (100) + C (100) + C (100) = 800
- Change CCLXV into a number. Do the same.CCLXV = C (100) + C (100) + L (50) + X (10) + V (5) = 265
- Do the calculation. Use our normal numbers.800 − 265 = 535
- Change the answer back to Roman numerals. Thousands, hundreds, tens, then ones.535 = D + XXX + V = DXXXV
Check. Read DXXXV again: 500 + 10 + 10 + 10 + 5 = 535. ✓
Watch out. Roman numerals are hard to add directly. Change them to numbers first.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numerals into numbers, do the calculation, then change the answer back into Roman numerals.
- Change CMXC into a number. Split it into groups and add.CMXC = CM (1000 − 100) + XC (100 − 10) = 990
- Change DLX into a number. Do the same.DLX = D (500) + L (50) + X (10) = 560
- Do the calculation. Use our normal numbers.990 − 560 = 430
- Change the answer back to Roman numerals. Thousands, hundreds, tens, then ones.430 = CD + XXX = CDXXX
Check. Read CDXXX again: 400 + 10 + 10 + 10 = 430. ✓
Watch out. Roman numerals are hard to add directly. Change them to numbers first.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numeral into a year in digits, then take it away from the later year.
- Change MCMXCIV into a year. Split it into groups and add.MCMXCIV = M (1000) + CM (1000 − 100) + XC (100 − 10) + IV (5 − 1) = 1994
- Decide which year is later. The later year is the bigger number. We take the earlier year away from it.1994 < 2026
- Subtract from the later year. 2026 is the later year.2026 − 1994 = 32
Check. 1994 + 32 = 2026. ✓
Watch out. Write the years as ordinary numbers before you subtract.
Method. Change both Roman numerals into numbers. Then take away to find how much longer.
- Change CCCLXXV to a number. CCC = 300, L = 50, XX = 20 and V = 5.CCCLXXV = 300 + 50 + 20 + 5 = 375
- Change DXL to a number. D = 500 and XL = 50 − 10 = 40.DXL = 500 + 40 = 540
- Find the difference. The second road is longer, so take the shorter from the longer.540 − 375 = 165 km
Check. 375 + 165 = 540. ✓
Watch out. Write both lengths as ordinary numbers before you take away.
Method. Work out each number properly using the rules: thousands, hundreds, tens, then ones.
- Write 1,999. 1,999 = 1,000 + 900 + 90 + 9.M + CM + XC + IX = MCMXCIX
- Write 490. 490 = 400 + 90.CD + XC = CDXC
- Say what went wrong. Tom took 1 away from 1,000 and 10 away from 500. But I can only go in front of V or X, and X can only go in front of L or C. So each part must be written separately.The correct numerals are MCMXCIX and CDXC.
Check. 1,000 + 900 + 90 + 9 = 1,999 and 400 + 90 = 490. ✓
Watch out. Break the number into thousands, hundreds, tens and ones. Write each part, then join them.
Method. Check each numeral against the rules. Rule 1: never more than three of the same symbol in a row. Rule 2: only I, X and C are taken away, and only from the next two bigger symbols.
- Check each numeral. Look at the repeats and at the small symbols in front of bigger ones.XXXX: wrong
MCMXCIX: correct (= 1,999)
VX: wrong
XCIV: correct (= 94)
IL: wrong - Explain each mistake. Use the rules.XXXX: There are four Xs in a row. We never write more than three of the same symbol in a row. 40 is XL.
VX: V (5) is never taken away from another symbol. Only I, X and C go in front to take away. 5 is just V.
IL: I can only go in front of V or X. To make 49 you write 40 + 9 = XL + IX = XLIX. - Write the answer. XXXX, VX and IL
Check. MCMXCIX = 1,999 and XCIV = 94 are both written correctly. ✓
Watch out. A short numeral can be correct and a short numeral can be wrong. Check the rules, not the length.
Method. The thousands, hundreds, tens and ones each use the most letters when they have the most repeated symbols. Think about which hundreds, tens and ones are longest.
- Thousands. Every year from 1000 to 1999 starts with just M. The years 2000 to 2026 start with MM, but they have no hundreds and only small tens, so they are short (7 letters at most). So the longest year is between 1000 and 1999.M = 1 letter
- Hundreds. DCCC (800) has 4 letters. No other hundreds digit has more.DCCC = 4 letters
- Tens. LXXX (80) has 4 letters.LXXX = 4 letters
- Ones. VIII (8) has 4 letters.VIII = 4 letters
- Put them together. Add the letters.1 + 4 + 4 + 4 = 13 → MDCCCLXXXVIII (1888)
Check. Only 1888 gives 13 letters. The next longest years, like 1878, have 12 letters. ✓
Watch out. Numerals with a 4 or a 9 (like IV or CM) are short. The longest use 8s.
Solving number and practical problems
Printable: Worksheet (PDF) · Answers (PDF) · Open this lesson on its own page
Now you can put everything together. Problems about big numbers can use place value, ordering, counting in powers of 10, rounding, negative numbers and Roman numerals. Here is a plan that works for every problem.
- Read the problem twice. Underline the numbers and the question.
- Picture it. Draw a number line, a table, a chart or a bar model.
- Choose what to do: count on, compare, round, add or take away.
- Work it out one step at a time.
- Check: does the answer make sense? Use an estimate.
Look at the bar chart. Always read the scale and the labels before you answer. The numbers on the bars are exact, so you can round them, compare them and find differences.
Key words. A clue is a fact that helps you find an unknown number. When a problem has several clues, use them one at a time and cross out the numbers that do not fit.
Key ideas
- Plan: read, picture, choose, work out, check.
- Round the real numbers, not numbers that have already been rounded.
- With clues, start with the clue that gives the most information.
- Use an estimate to check that an answer is sensible.
- Say what your answer means (units, names, years).
Method. Round every number to the nearest 100,000. Then see which ones are the same.
- Round each number. Look at the ten thousands digit each time: 5 or more rounds up, 4 or less rounds down.Park A: 245,000 (digit 4) ≈ 200,000
Park B: 318,500 (digit 1) ≈ 300,000
Park C: 287,000 (digit 8) ≈ 300,000
Park D: 96,200 (digit 9) ≈ 100,000 - Find the numbers that are the same. Park B and Park C both round to 300,000.
- Write the answer. Park B and Park C
Check. The other parks round to different numbers. ✓
Watch out. Round the real numbers, not the rounded ones, each time.
Method. First find the range of numbers that round to 600,000. Then use the cards to make the largest number in that range.
- Find the range for 600,000. To the nearest 100,000, the numbers that round to 600,000 go from 550,000 to 649,999.550,000 to 649,999
- Choose the first digit. The number must be at most 649,999, so the first digit is 6.First digit = 6
- Choose the next digit. The number must still be at most 649,999, so the second digit has to be 4 or less. Take the biggest card that fits.Second digit = 3
- Put the other cards in order, biggest first. This makes the number as big as possible.638,510
Check. 638,510 is between 550,000 and 649,999 and uses every card once. ✓
Watch out. Check your answer rounds to the right number.
Rounded to the nearest 100,000 it is 400,000.
Rounded to the nearest 10,000 it is 350,000.
The thousands digit is 4.
The tens digit and ones digit are the same. The hundreds digit is 2 more than the ones digit.
The digits add up to 26.
What is the number?
Method. Use the rounding clues first to find the range. Then use the digit clues.
- Use the clue about 10,000. To round to 350,000 the number is from 345,000 to 354,999.345,000 to 354,999
- Use the clue about 100,000. To round to 400,000 the number must be at least 350,000. Together with the first clue:350,000 to 354,999. So the number starts 35 and the thousands digit is 0 to 4.
- Use the thousands digit. The thousands digit is 4.354,…
- Use the last three digits. Let the ones digit be o. The tens digit is o and the hundreds digit is o + 2. The digits 3, 5, 4 add to 12, so 12 + (o + 2) + o + o = 26.14 + 3o = 26
3o = 12, so o = 4 - Write the number. Ones 4, tens 4, hundreds 6.354,644
Check. 354,644 ≈ 350,000 (10,000) ✓, ≈ 400,000 (100,000) ✓, thousands 4 ✓, 4 = 4 and 6 = 4 + 2 ✓, 3+5+4+6+4+4 = 26 ✓
Watch out. Check your answer against every clue.
Method. Add 10,000 each month until the total is 300,000 or more.
- Start with the money now. Month 0.Month 0: £235,000
- Add £10,000 each month. Only the ten thousands digit changes.Month 1: £245,000
Month 2: £255,000
Month 3: £265,000
Month 4: £275,000
Month 5: £285,000
Month 6: £295,000
Month 7: £305,000 - Find the first total of 300,000 or more. Month 6 is £295,000, which is not enough. Month 7 is £305,000.7 months
Check. 235,000 + 7 × 10,000 = 305,000, which is at least 300,000. ✓
Watch out. £295,000 is close, but it is less than £300,000, so it is not enough.
Method. Do the moves one at a time. Going up adds. Going down takes away.
- Start position. Below sea level is negative.−24 m
- Swim up 9 m. Going up makes the number bigger.−24 m up 9 m: start below zero and go up 9 m → −15 m
- Dive down 15 m. Going down makes the number smaller.−15 m down 15 m: start at or below zero and go down 15 m more → −30 m
- Write the answer. The question asks how far below sea level, so give the depth.She is at −30 m, which is 30 m below sea level.
Check. Total change = +9 − 15 = −6. −24 − 6 = −30. ✓
Watch out. Take the moves in order and watch which way each one goes.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numeral to a year, then round it.
- Change MDCCLXXXIX to a number. M = 1,000, D = 500, CC = 200, LXXX = 80, IX = 9.1,000 + 500 + 200 + 80 + 9 = 1789
- Look at the tens digit. Rounding to the nearest 100 means looking at the tens digit.1789: tens digit is 8, which is 5 or more, so round up
- Round. The hundreds go up by 1.1789 ≈ 1800
Check. 1,789 is 11 away from 1,800 and 89 away from 1,700. 1,800 is nearer. ✓
Watch out. Write the year in digits first, then round.
Key words. < means “less than” and > means “greater than”. The wide end of the sign faces the bigger number.
Method. Compare the digits from the left, one column at a time. The first column that is different tells you which number is bigger.
- Write each side as one number. We can only compare numbers when they are written the usual way.sixty-two thousand and four = 62,004
62,040 = 62,040 - Write both numbers in a place-value table. Lining up the columns lets us compare digit by digit.
Thousands Ones TTh Th H T O 62,004 6 2 0 0 4 62,040 6 2 0 4 0 - Compare the digits from the left. The first column where they are different decides which number is bigger.ten thousands: 6 and 6 are the same, so look at the next column.
thousands: 2 and 2 are the same, so look at the next column.
hundreds: 0 and 0 are the same, so look at the next column.
tens: 0 and 4 are different. 0 < 4, so 62,004 is smaller. - Write the correct symbol. < means “is less than”, > means “is greater than”, = means “is equal to”.62,004 < 62,040
Check. Picture a number line: 62,004 is to the left of 62,040. ✓
Watch out. Start at the LEFT (the biggest column). Do not start with the ones.
Watch out
Do not stop when you have a number. Check that it answers the question (for example “how many months” or “how far below sea level”), and check it against every clue. Remember to round the real numbers, never numbers that are already rounded.Exercise 1G Problems and puzzles
Non-calculatorMethod. Compare the numbers on the bars. The biggest bar is the park with the most visitors.
- Read each bar. The exact numbers are written on the bars.Park A: 245,000
Park B: 318,500
Park C: 287,000
Park D: 96,200 - Compare from the left. Compare the hundred thousands digits: 2, 3, 2, 0. Park B has the biggest.318,500 > 287,000 > 245,000 > 96,200
- Write the answer. Park B
Check. 318,500 has a 3 in the hundred thousands column. The others have 2 or fewer digits there. ✓
Watch out. Read the numbers on the bars, not just the heights.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 96,200 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.90,000 < 96,200 < 100,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 6.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.96,200 ≈ 100,000 (to the nearest 10,000)
Check. Distances: 96,200 − 90,000 = 6,200 and 100,000 − 96,200 = 3,800. 100,000 is the nearer one. ✓
Watch out. A 9 can carry: when you round up a 9 it becomes 10, so the next digit goes up too.
Method. Round every number to the nearest 100,000. Then see which ones are the same.
- Round each number. Look at the ten thousands digit each time: 5 or more rounds up, 4 or less rounds down.Park A: 245,000 (digit 4) ≈ 200,000
Park B: 318,500 (digit 1) ≈ 300,000
Park C: 287,000 (digit 8) ≈ 300,000
Park D: 96,200 (digit 9) ≈ 100,000 - Find the numbers that are the same. Park B and Park C both round to 300,000.
- Write the answer. Park B and Park C
Check. The other parks round to different numbers. ✓
Watch out. Round the real numbers, not the rounded ones, each time.
Method. First find the range of numbers that round to 500,000. Then use the cards to make the largest number in that range.
- Find the range for 500,000. To the nearest 100,000, the numbers that round to 500,000 go from 450,000 to 549,999.450,000 to 549,999
- Choose the first digit. The number must be at most 549,999, so the first digit is 5.First digit = 5
- Choose the next digit. The number must still be at most 549,999, so the second digit has to be 4 or less. Take the biggest card that fits.Second digit = 4
- Put the other cards in order, biggest first. This makes the number as big as possible.549,820
Check. 549,820 is between 450,000 and 549,999 and uses every card once. ✓
Watch out. Check your answer rounds to the right number.
Rounded to the nearest 100,000 I am 800,000.
Rounded to the nearest 10,000 I am 840,000.
Rounded to the nearest 1,000 I am 838,000.
My hundreds digit is 4.
My tens digit is double my ones digit, and my ones digit is not 0.
My digits add up to 35.
What number am I?
Method. Use the rounding clues to find the range. Then use the digit clues.
- Use the clue about 1,000. To round to 838,000, the number is from 837,500 to 838,499.837,500 to 838,499
- Check the other rounding clues. 838,000 rounds to 840,000 (10,000) and 800,000 (100,000), so these clues are already true.Range stays 837,500 to 838,499
- Use the hundreds digit. It is 4, so the number is in the range 838,400 to 838,499.838,4_ _
- Use the tens and ones clues. The tens digit is double the ones digit. Try ones digits 1 to 4.ones 1: tens 2: number 838,421, digit total 26
ones 2: tens 4: number 838,442, digit total 29
ones 3: tens 6: number 838,463, digit total 32
ones 4: tens 8: number 838,484, digit total 35 - Use the digit total. The digits add up to 35.Only ones 4 gives a total of 35: 838,484
Check. 838,484: 800,000 ✓, 840,000 ✓, 838,000 ✓, hundreds 4 ✓, tens 8 = 2 × 4 ✓, 8+3+8+4+8+4 = 35 ✓
Watch out. Cross out numbers that do not fit as you use each clue.
Method. Count on in 1,000s, one year at a time. Each year is one jump.
- Say what each jump is. Each year, the amount goes up by 1,000.1 year = +1,000
- Count 5 jumps. Start each jump from the number you have just found.Year 1: 62,500 + 1,000 = 63,500
Year 2: 63,500 + 1,000 = 64,500
Year 3: 64,500 + 1,000 = 65,500
Year 4: 65,500 + 1,000 = 66,500
Year 5: 66,500 + 1,000 = 67,500 - Write the answer. 67,500 seats
Check. 5 × 1,000 = 5,000 and 62,500 + 5,000 = 67,500. ✓
Watch out. Count the jumps carefully. Tally marks can help you keep track.
Method. To find 10,000 less, change the ten thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the ten thousands digit. 10,000 is one ten thousand, so we change the ten thousands digit.
Thousands Ones TTh Th H T O 6 7 5 0 0 - Take 1 from the ten thousands digit. 10,000 less means 1 less ten thousand.6 − 1 = 5 ten thousands
- Write the new number. The digits that did not change stay the same.67,500 − 10,000 = 57,500
Check. Do the opposite: 57,500 + 10,000 = 67,500. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. Draw a number line, start at −15 and jump down 15. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 15. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.−15 down 15: start at or below zero and go down 15 more → −30
- Write the answer. This is the new depth.−30 m
Check. Do the opposite: −30 + 15 = −15. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. Find how far apart the two depths are on a number line. Both are below zero.
- Write the depths. The first diver is at −30 m (from part a).−30 m and −11 m
- Find the difference. Both are below zero, so take the smaller distance from the bigger.30 − 11 = 19
- Write the answer. 19 m deeper
Check. −11 − 19 = −30. ✓
Watch out. The difference is how far apart they are. It is never negative.
Key words. An estimate is a sensible answer that is close to the exact one. We find it by rounding first.
Method. Round both numbers to the nearest 1,000, then do the easy calculation.
- Round the first number. Look at the digit just to the right of the thousands column.4,980 ≈ 5,000
- Round the second number. Do the same.5,120 ≈ 5,000
- Do the easy calculation. Rounded numbers are quick to add and take away.5,000 + 5,000 = 10,000
Check. The exact answer is 10,100, which is close to 10,000. ✓
Watch out. An estimate is not exact. It tells you roughly how big the answer should be.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Change the Roman numeral to a year, then round it.
- Change MDCCLXXXIX to a number. M = 1,000, D = 500, CC = 200, LXXX = 80, IX = 9.1,000 + 500 + 200 + 80 + 9 = 1789
- Round to the nearest 100. The tens digit is 8, so round up.1789 ≈ 1800
- Write the answer. 1800
Check. 1,800 is only 11 from 1,789. ✓
Watch out. Write the year in digits first, then round.
Method. Find the numbers that could be the real crowd for each newspaper, then see if they overlap.
- Second newspaper. To the nearest 1,000 the crowd is 84,000, so it is from 83,500 to 84,499.83,500 to 84,499
- First newspaper. To the nearest 10,000 the crowd is 80,000, so it is from 75,000 to 84,999.75,000 to 84,999
- Compare. All the numbers from 83,500 to 84,499 are also in the range 75,000 to 84,999.Yes, both can be correct. For example, a crowd of 84,000 rounds to 84,000 and also to 80,000.
Check. 84,000: the thousands digit is 4, so it rounds down to 80,000. ✓
Watch out. Different amounts of rounding can give different numbers for the same crowd.
Method. Write each one as a number and find the one that does not match.
- Write each as a number. Use place value or the Roman numeral rules.1,000 + 200 + 5 = 1,205
1,250
MCCV = 1,000 + 200 + 5 = 1,205
one thousand, two hundred and five = 1,205 - Compare them. Three are 1,205 and one is 1,250.1,205, 1,250, 1,205, 1,205
- Write the odd one out. 1,250
Check. 1,250 has 5 tens. The others have 5 ones. ✓
Watch out. Look at which column the 5 is in.
“When you round a number to the nearest 100, the answer is bigger than the number.”
Method. Try rounding some numbers and compare each answer with the number you started with.
- Try 6,280. The tens digit is 8, so round up.6,280 ≈ 6,300. 6,300 is bigger. It works.
- Try 6,220. The tens digit is 2, so round down.6,220 ≈ 6,200. 6,200 is smaller. It does not work.
- Try 6,300. This is already a multiple of 100.6,300 ≈ 6,300. The same. It does not work.
- Write the answer. It works for some numbers only.Sometimes
Check. Rounding up makes a number bigger, and rounding down makes it smaller. ✓
Watch out. Rounding does not always make a number bigger.
Method. The number must be less than 550,000. Build it from the left, using the biggest digit that fits each time, and never repeat a digit.
- Find the range. To round to 500,000, the number is from 450,000 to 549,999.450,000 to 549,999
- First digit. The biggest first digit that fits is 5.First digit = 5
- Second digit. It must be 4 or less, so that the number is under 550,000. It cannot be 5 because the digits must all be different. The biggest choice is 4.5 4 _ _ _ _
- The other four digits. Use the biggest digits left: 9, 8, 7, 6.5 4 9 8 7 6
- Write the number. 549,876
Check. 549,876 is less than 550,000 and uses six different digits. ✓
Watch out. Check that no digit is used twice.
Chapter summary
| Skill | Method |
|---|---|
| Read and write large numbers | Split into periods with commas: Millions | Thousands | Ones. Zeros are place holders. 999,999 + 1 = 1,000,000. |
| Value of a digit | Digit × value of its column. The 4 in 340,000 is worth 40,000. Partition: 306,075 = 300,000 + 6,000 + 70 + 5. |
| Compare and order | More digits means bigger. Same digits: compare from the left. < less than, > greater than. |
| Counting in powers of 10 | Only one digit changes (the column that matches the step). Carry for a 9 going up, swap for a 0 going down. |
| Missing terms | Find two known numbers, divide the difference by the number of jumps, then fill the gaps. |
| Negative numbers | Below zero. Further left is smaller. Split jumps that cross zero. Difference across zero: add the distances. |
| Rounding | Look at the digit to the right. 5 or more: round up. 4 or less: round down. Halfway rounds up. |
| Estimating | Round each number, then calculate. Use the estimate to check an answer. |
| Roman numerals | I 1, V 5, X 10, L 50, C 100, D 500, M 1,000. Thousands, hundreds, tens, ones. MCMXCIX = 1,999, MMXXVI = 2,026. |
Can you…?
- I can read, write and partition numbers up to 1,000,000.
- I can say the value of any digit.
- I can order and compare numbers up to 1,000,000.
- I can count on and back in 10s, 100s, 1,000s, 10,000s and 100,000s, and fill missing numbers.
- I can use negative numbers for temperatures, depths and bank balances and count through zero.
- I can round to the nearest 10, 100, 1,000, 10,000 and 100,000.
- I can use rounding to estimate and to check answers.
- I can read Roman numerals up to 1,000 and years such as MMXXVI.
- I can solve problems and puzzles that use all of these ideas.
Key terms
- Period
- A group of three columns in a big number: Ones, Thousands, Millions.
- Digit
- One of the symbols 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.
- Place value
- The value of a digit depends on its column.
- Place holder
- A zero that holds an empty column so the other digits stay in the right place.
- Partition
- To split a number into the value of each digit: 4,306 = 4,000 + 300 + 6.
- Ascending
- Getting bigger: smallest first.
- Descending
- Getting smaller: biggest first.
- Power of 10
- The numbers 10, 100, 1,000, 10,000, 100,000 and so on. Each is 10 times the one before.
- Sequence
- A list of numbers that follow a rule.
- Negative number
- A number less than zero, written with a minus sign, like −5.
- Overdrawn
- A bank balance below zero. You owe the bank money.
- Round
- To change a number to a nearby, simpler number, such as to the nearest 1,000.
- Estimate
- A sensible answer that is close to the exact one.
- Roman numerals
- Letters used for numbers by the Romans: I, V, X, L, C, D, M.
Exercise 1Z Check-up (non-calculator)
Non-calculatorKey words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. The value of a digit depends on its column. Find the column, then multiply the digit by the value of the column.
- Write the number in a place-value table. Each column has a name and a value. The coloured digit is the one we want.
Thousands Ones HTh TTh Th H T O 2 4 5 3 1 0 - Find which column the digit is in. The digit is 4 and it sits in the ten thousands column.1 ten thousand = 10,000
- Multiply the digit by the value of the column. There are 4 ten thousands.4 × 10,000 = 40,000
Check. Say it in words: 4 ten thousands is forty thousand. ✓
Watch out. The digit is 4 but its value is 40,000. The same digit is worth different amounts in different columns.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Say the number in parts, from left to right: the thousands period first, then the hundreds, then the last two digits.
- Write the number in a place-value table. The comma splits the digits into the Thousands period and the Ones period.
Thousands Ones HTh TTh Th H T O 3 0 5 0 8 0 - Read each part and say it in words. Say the thousands period as a number and then add the word thousand.Thousands period: 305 → three hundred and five thousand
Last two digits: 80 → eighty - Join the parts together. Put “and” before the last two digits (the tens and ones) when there are hundreds or thousands before them.three hundred and five thousand and eighty
Check. Read it out loud. It sounds like 305,080. ✓
Watch out. Zeros are never said aloud. 400,060 is “four hundred thousand and sixty”: nothing is said for the empty columns, but they still need a 0 when you write the digits.
Method. To find 10,000 less, change the ten thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the ten thousands digit. 10,000 is one ten thousand, so we change the ten thousands digit.
Thousands Ones HTh TTh Th H T O 2 1 5 0 0 0 - Take 1 from the ten thousands digit. 10,000 less means 1 less ten thousand.1 − 1 = 0 ten thousands
- Write the new number. The digits that did not change stay the same.215,000 − 10,000 = 205,000
Check. Do the opposite: 205,000 + 10,000 = 215,000. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Smallest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 472,510 4 7 2 5 1 0 427,510 4 2 7 5 1 0 472,150 4 7 2 1 5 0 47,251 4 7 2 5 1 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.47,251 and 427,510: 427,510 has 6 digits and 47,251 has 5 digits, so 427,510 is bigger.
427,510 and 472,150: ten thousands: 2 and 7 are different. 2 < 7, so 427,510 is smaller.
472,150 and 472,510: hundreds: 1 and 5 are different. 1 < 5, so 472,150 is smaller. - Write them smallest first. Check you have used every number once.47,251, 427,510, 472,150, 472,510
Check. Count the numbers: 4 in the question and 4 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Key words. Counting in steps of 10,000 means taking away 10,000 again and again. 10, 100, 1,000, 10,000 and 100,000 are powers of 10.
Method. Counting back in 10,000s means taking away 10,000 each time. Only the ten thousands digit changes (unless we carry or swap).
- Find the size of each jump. We are counting back in steps of 10,000, which is 1 ten thousand.Each jump is −10,000.
- Work out the numbers one jump at a time. Always start from the number you have just found.305,000 − 10,000 = 295,000 (0 ten thousands: swap 1 from the next column for 10 ten thousands, then take 1 ten thousand away)
295,000 − 10,000 = 285,000 (the ten thousands digit goes 9 → 8)
285,000 − 10,000 = 275,000 (the ten thousands digit goes 8 → 7) - Write the numbers in order. 295,000, 285,000, 275,000
Check. Go the other way from the last number: 275,000 + 10,000 = 285,000. ✓
Watch out. Only the ten thousands digit changes, unless it is a 9 going up (carry) or a 0 going down (swap). Check the digit before every jump.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 10,000 that 683,472 is between. Rounding to the nearest 10,000 means choosing the closest multiple of 10,000.680,000 < 683,472 < 690,000
- Look at the thousands digit (the digit just to the right of the ten thousands digit). This digit tells us if we are past halfway.The thousands digit is 3.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.3 is 4 or less, so round down.
- Write the rounded number. All the digits to the right of the ten thousands column become zeros.683,472 ≈ 680,000 (to the nearest 10,000)
Check. Distances: 683,472 − 680,000 = 3,472 and 690,000 − 683,472 = 6,528. 680,000 is the nearer one. ✓
Watch out. Only the digit just to the right decides. Do not look at digits further along.
Method. Draw a number line, start at 3 and jump down 8. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go down 8. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.3 down 8: go down 3 to reach 0, then 5 more below zero → −5
- Write the answer. This is the new temperature.−5°C
Check. Do the opposite: −5 + 8 = 3. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Method. On a number line, numbers further to the left are smaller. Mark each number, then read them off from left to right.
- Put the numbers on a number line. The line shows which are below zero.
- Read from left to right. Left is smallest, right is biggest.−10, −6, −1, 2
- Write them smallest first. Check you have used every number once.−10, −6, −1, 2
Check. The numbers below zero are the smallest. Of those, the one with the biggest digit (like −9) is furthest from zero, so it is the smallest. ✓
Watch out. −9 is smaller than −2. The further below zero, the smaller the number.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the number into thousands, hundreds, tens and ones. Write each part in Roman numerals, then put them side by side (biggest first).
- Split the number into thousands, hundreds, tens and ones. Roman numerals are built one part at a time, biggest first.474 = 400 + 70 + 4
- Write 400 in Roman numerals. D is 500; 400 is CD (100 before 500) and 900 is CM (100 before 1,000).400 = CD
- Write 70 in Roman numerals. 40 is XL (10 before 50) and 90 is XC (10 before 100).70 = LXX
- Write 4 in Roman numerals. 4 is IV (1 before 5) and 9 is IX (1 before 10).4 = IV
- Put the parts side by side, biggest first. Thousands on the left, then hundreds, tens and ones.CD + LXX + IV = CDLXXIV
Check. Read it back: 400 + 50 + 10 + 10 + 4 = 474. ✓
Watch out. Never write the same symbol more than three times in a row. 4 is IV, not IIII; 40 is XL; 400 is CD; 900 is CM.
Key words. Roman numerals are letters used for numbers: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. A small symbol before a bigger one is taken away; after it is added.
Method. Split the Roman numeral into groups, write the value of each group, then add them up.
- Split the numeral into groups, reading from the left. A small symbol in front of a bigger one (like CM, XC or IV) is taken away. Otherwise just add.M = 1,000
CM = 1000 − 100 = 900 (small symbol in front, so take it away)
L = 50
X = 10
X = 10
X = 10
V = 5
I = 1
I = 1
I = 1 - Add the values. Add the biggest groups first.1,000 + 900 + 50 + 10 + 10 + 10 + 5 + 1 + 1 + 1 = 1,988
- Write the answer. 1988
Check. Write 1,988 in Roman numerals: M + CM + LXXX + VIII = MCMLXXXVIII. ✓
Watch out. Read from the left. A small symbol is only taken away when it comes BEFORE a bigger one: IX is 9 but XI is 11.
Total 17 marks. Allow about 17 minutes.
Exercise 1X SATs-style questions
Non-calculatorMethod. To find 10,000 more, change the ten thousands digit by 1. Look out for 9s going up (carrying) and 0s going down (swapping).
- Find the ten thousands digit. 10,000 is one ten thousand, so we change the ten thousands digit.
Thousands Ones HTh TTh Th H T O 3 9 6 5 0 0 - Add 1 to the ten thousands digit. There are 9 ten thousands. 1 more ten thousand makes 10 ten thousands, which is 1 of the next column and 0 ten thousands. We carry (and the carry carries on if the next digit is also 9).9 + 1 = 10 → write 0 in the TTh column and carry 1
- Write the new number. The digits that did not change stay the same.
Thousands Ones HTh TTh Th H T O 396,500 3 9 6 5 0 0 406,500 4 0 6 5 0 0
396,500 + 10,000 = 406,500
Check. Do the opposite: 406,500 − 10,000 = 396,500. ✓
Watch out. Only the digit in the column you are working on changes, unless you carry or swap. Do not change all the digits.
Method. The thousands column is the fourth from the right. Look at each number.
- Find the thousands digit in each number. The thousands column is the fourth digit from the right.24,600: thousands digit is 4
60,450: thousands digit is 0
604,500: thousands digit is 4
546,000: thousands digit is 6 - Choose the number with 6 thousands. 546,000
Check. 546,000 = 500,000 + 40,000 + 6,000. The 6 is worth 6,000. ✓
Watch out. 604,500 has a 6 in the hundred thousands column, not the thousands column.
Key words. A digit is one of 0 to 9. The value of a digit is what it is worth. A period is a group of three columns: Ones, Thousands, Millions.
Method. Listen for the words “thousand” and “hundred”. They tell you which period and column each part goes in.
- Split the words into parts. Each part belongs to one period or column.“two hundred and six thousand” → the Thousands period is 206
no hundreds are said → 0 in the hundreds column
“forty” → 4 in the tens column and 0 in the ones column - Write the digits in a place-value table. Write a zero in every column that was not mentioned. Each period has three digits (except the first).
Thousands Ones HTh TTh Th H T O 2 0 6 0 4 0 - Write the number. Put a comma between the periods.206,040
Check. Say 206,040 in words: two hundred and six thousand and forty. It matches. ✓
Watch out. A zero is a place holder. Without it the digits slip into the wrong columns and the number changes.
Key words. To round a number is to change it to a nearby number that is easier to use. ≈ means “is about equal to”.
Method. Look at the digit to the right of the one you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
- Find the two multiples of 100 that 74,950 is between. Rounding to the nearest 100 means choosing the closest multiple of 100.74,900 < 74,950 < 75,000
- Look at the tens digit (the digit just to the right of the hundreds digit). This digit tells us if we are past halfway.The tens digit is 5.
- Decide: round up or round down? 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up.
- Write the rounded number. All the digits to the right of the hundreds column become zeros.74,950 ≈ 75,000 (to the nearest 100)
Check. Distances: 74,950 − 74,900 = 50 and 75,000 − 74,950 = 50. 75,000 is the one we choose when exactly halfway (halfway rounds up). ✓
Watch out. Only look at the digit just to the right. Do not round twice. Halfway always rounds up.
346,200, 347,200, ?, ?, 350,200[2 marks]
Method. Find the size of one jump from two numbers you can see. Then use it to fill the gaps.
- Find two numbers you know and count the jumps between them. Each jump in the sequence is the same size.From 346,200 to 347,200 is 1 jump.
The difference is 1,000. - Say which way and how big each jump is. The numbers are getting bigger, so we count on.Each jump is +1,000.
- Fill in the missing numbers. Add (or take away) one jump from a number you know. Where two gaps are side by side, fill one first and use it for the next.Number 3: 347,200 + 1,000 = 348,200
Number 4: 348,200 + 1,000 = 349,200 - Write the missing numbers. Put them in the order they appear.348,200, 349,200
Check. Read the whole sequence again and check every jump is +1,000: 346,200, 347,200, 348,200, 349,200, 350,200. ✓
Watch out. Do not just look at the first two numbers. Check the jump is the same all the way along.
Method. Draw a number line, start at −7 and jump up 12. When you pass 0 the numbers change between positive and negative.
- Show the start on a number line. This lets us see where zero is.
- Go up 12. Split the jump into two parts if it crosses zero: the part that reaches 0, then the part that goes past it.−7 up 12: go up 7 to reach 0, then 5 more → 5
- Write the answer. This is the new temperature.5°C
Check. Do the opposite: 5 − 12 = −7. ✓
Watch out. Going down past zero gives a negative number. Going up from a negative number gets closer to zero.
Key words. Ascending order means smallest first. Descending order means biggest first.
Method. Put the numbers in a place-value table, then compare columns from the left. Smallest first.
- Write all the numbers in a place-value table. This lines up the digits so we can compare them.
Thousands Ones HTh TTh Th H T O 530,800 5 3 0 8 0 0 508,300 5 0 8 3 0 0 538,000 5 3 8 0 0 0 503,800 5 0 3 8 0 0 - Compare the numbers in pairs, from the left. Where the digits in a column match, move on to the next column.503,800 and 508,300: thousands: 3 and 8 are different. 3 < 8, so 503,800 is smaller.
508,300 and 530,800: ten thousands: 0 and 3 are different. 0 < 3, so 508,300 is smaller.
530,800 and 538,000: thousands: 0 and 8 are different. 0 < 8, so 530,800 is smaller. - Write them smallest first. Check you have used every number once.503,800, 508,300, 530,800, 538,000
Check. Count the numbers: 4 in the question and 4 in the answer. ✓
Watch out. Tick each number off as you write it, so you do not miss one.
Method. Change both Roman numerals into years. Then take the earlier year away from the later year.
- Change MCMXCVIII to a year. M = 1,000, CM = 900, XC = 90, VIII = 8.1,000 + 900 + 90 + 8 = 1998
- Change MMXXV to a year. MM = 2,000, XX = 20, V = 5.2,000 + 20 + 5 = 2025
- Find the difference. Take the earlier year from the later year.2025 − 1998 = 27
Check. 1998 + 27 = 2025. ✓
Watch out. 2 marks: 1 for changing both numerals correctly and 1 for the right difference.
Method. Round 98,000 to the nearest 100,000 and compare it with Amira’s answer.
- Find the two hundred thousands either side. The multiples of 100,000 either side of 98,000 are 0 and 100,000.0 < 98,000 < 100,000
- Look at the ten thousands digit. It is 9, which is 5 or more, so round up.98,000 ≈ 100,000
- Answer Amira. Amira’s answer, 90,000, is not a multiple of 100,000, so it cannot be the answer to this question.No. 98,000 rounds to 100,000.
Check. 98,000 is only 2,000 from 100,000. It is 98,000 from 0. ✓
Watch out. 2 marks: 1 for rounding correctly and 1 for explaining that the ten thousands digit is 9.
Rounded to the nearest 100,000 it is 500,000.
Rounded to the nearest 10,000 it is 450,000.
What is the smallest number Sam could be thinking of? What is the largest? Show how you know.[3 marks]
Method. Use each clue to find a range of numbers. Then see where the two ranges overlap.
- Use the nearest 100,000 clue. To round to 500,000 the number is from 450,000 to 549,999.450,000 to 549,999
- Use the nearest 10,000 clue. To round to 450,000 the number is from 445,000 to 454,999.445,000 to 454,999
- Find where the ranges overlap. The number must fit both clues.The overlap is 450,000 to 454,999
- Write the smallest and largest. Smallest 450,000, largest 454,999
Check. 449,999 rounds to 400,000 (nearest 100,000) and 455,000 rounds to 460,000 (nearest 10,000), so neither works. ✓
Watch out. 3 marks: 1 for each range, 1 for both answers.