Place value to a million and decimals to tenths
By the end of this chapter you will be able to
- Say the value of each digit in a number to 1,000,000
- Read and write big numbers in numerals and words
- Find 10,000 more or less, and round big numbers
- Read and write tenths as decimals
- Compare and order decimals to tenths
You should already know
- Numbers to 10,000 and their place value (Level 4, chapter 1)
- Rounding to the nearest 10, 100 and 1000 (Level 4, chapter 2)
Where this leads
- Adding and subtracting whole numbers to a million (chapter 2)
- Decimals to hundredths (chapter 7)
Step-by-step practice: maths (Level 5). Small steps, repeated until fluent. Content: Read, write, order and compare numbers to 1,000,000 and know the value of each digit (Y5 paraphrase), Round any whole number to the nearest 10, 100, 1000, 10000 or 100000 (Y5 paraphrase), Recognise and write decimals as tenths, and place them on a number line (Y4 paraphrase), Compare and order decimals to tenths (Y4 paraphrase).
Exercise P Do you remember?
Non-calculatorMethod. The 6 is in the hundreds column, so its value is 6 hundreds.
- Find the hundreds column. Count from the right: ones, tens, hundreds.Hundreds column
- Multiply the digit by 100. Each hundreds place is worth 100.6 × 100 = 600
- Write the value. This is the value of the 6.600
Check. Check: 600 is 6 groups of 100.
Watch out. The value is 600, not 6.
Method. Read the thousands, then the rest.
- Say the thousands. Seven thousand.7 thousand
- Say the rest. Two hundred and six.206 = two hundred and six
- Put them together. Join the two parts.seven thousand and two hundred and six
Check. Check: 7,000 + 200 + 6 = 7,206.
Watch out. Use the word and before the tens and ones.
Method. Use the 8 times table.
- Count in eights nine times. Each count adds 8.8, 16, 24, 32, 40, 48, 56, 64, 72
- The last number we said is the answer. We counted nine groups of 8.8 × 9 = 72
- Write the answer. This is the total.72
Check. Check: 72 ÷ 9 = 8.
Watch out. Count the eights carefully.
Method. Look at the tens digit to decide.
- Look at the tens digit. It decides whether to round up or down.Tens digit is 3
- Decide. 3 is 4 or less, so round down.3 is 4 or less
- Write the rounded number. Replace the tens and ones with zeros.4,700
Check. Check: 4,700 is the multiple of 100 closest to 4,736.
Watch out. Round down on a 4 or less.
Method. Work from left to right.
- Add 6,000 and 2,500. Add the thousands.6,000 + 2,500 = 8,500
- Take away 1,000. Subtract the thousand.8,500 - 1,000 = 7,500
- Write the answer. This is the final number.7,500
Check. Check: 7,500 + 1,000 = 8,500, and 8,500 - 2,500 = 6,000.
Watch out. Add and take away in order.
Digits and place value to a million
Each digit in a number has a value that depends on its column. In 472,893, the 4 is in the hundred thousands column, so it is worth 400,000. The 7 is in the ten thousands column, so it is worth 70,000.
Groups of three digits are separated by commas to make big numbers easier to read. Read the thousands, then the rest.
Key ideas
- Each column is ten times the column on its right.
- The value of a digit = the digit × the value of its column.
- Partitioning splits a number into the value of each digit.
Method. Read the column, then multiply the digit by the value of that column.
- Find the ten thousands column. Count the columns from the right: ones, tens, hundreds and so on.The digit is 7
- Multiply the digit by the value of its column. Each place in the ten thousands column is worth 10,000.7 × 10,000 = 70,000
- Write the value. This is the value of the digit in this number, not just the digit.70,000
Check. Check: 70,000 is 7 groups of 10,000.
Watch out. Say the value, such as 70,000, not only the digit 7.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.472 thousand and 893
- Say the thousands. Say the number before the thousand, then the word thousand.four hundred and seventy-two thousand
- Say the last three digits. Say them as a number up to 999.eight hundred and ninety-three
- Put the words together. Use a space between the two parts; use and before a number under 100.four hundred and seventy-two thousand eight hundred and ninety-three
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.400,000, 70,000, 2,000, 800, 90, 3
- Write the parts as an addition. Add the parts together to make the number.400,000 + 70,000 + 2,000 + 800 + 90 + 3
- Check by adding. Adding the parts again must give the number we started with.400,000 + 70,000 + 2,000 + 800 + 90 + 3
Check. Check: the parts add to 472,893.
Watch out. Leave out any digit that is zero. Zero adds nothing.
Watch out
Watch out. The 7 in 472,893 is worth 70,000, not 7. Name the column first, then multiply.
Exam tip
Grown-up tip. Ask the child to read a big number in parts: “472 thousand, 893.” Practise saying the value of each digit aloud.
Exercise 1A Practice: digits, words and partitioning
Non-calculatorMethod. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.500,000, 3,000, 900, 20, 4
- Write the parts as an addition. Add the parts together to make the number.500,000 + 3,000 + 900 + 20 + 4
- Check by adding. Adding the parts again must give the number we started with.500,000 + 3,000 + 900 + 20 + 4
Check. Check: the parts add to 503,924.
Watch out. Leave out any digit that is zero. Zero adds nothing.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.723 thousand and 202
- Say the thousands. Say the number before the thousand, then the word thousand.seven hundred and twenty-three thousand
- Say the last three digits. Say them as a number up to 999.two hundred and two
- Put the words together. Use a space between the two parts; use and before a number under 100.seven hundred and twenty-three thousand two hundred and two
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Read the column, then multiply the digit by the value of that column.
- Find the hundreds column. Count the columns from the right: ones, tens, hundreds and so on.The digit is 6
- Multiply the digit by the value of its column. Each place in the hundreds column is worth 100.6 × 100 = 600
- Write the value. This is the value of the digit in this number, not just the digit.600
Check. Check: 600 is 6 groups of 100.
Watch out. Say the value, such as 70,000, not only the digit 7.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.435 thousand and 751
- Say the thousands. Say the number before the thousand, then the word thousand.four hundred and thirty-five thousand
- Say the last three digits. Say them as a number up to 999.seven hundred and fifty-one
- Put the words together. Use a space between the two parts; use and before a number under 100.four hundred and thirty-five thousand seven hundred and fifty-one
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.672 thousand and 537
- Say the thousands. Say the number before the thousand, then the word thousand.six hundred and seventy-two thousand
- Say the last three digits. Say them as a number up to 999.five hundred and thirty-seven
- Put the words together. Use a space between the two parts; use and before a number under 100.six hundred and seventy-two thousand five hundred and thirty-seven
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.100,000, 60,000, 9,000, 200, 80, 6
- Write the parts as an addition. Add the parts together to make the number.100,000 + 60,000 + 9,000 + 200 + 80 + 6
- Check by adding. Adding the parts again must give the number we started with.100,000 + 60,000 + 9,000 + 200 + 80 + 6
Check. Check: the parts add to 169,286.
Watch out. Leave out any digit that is zero. Zero adds nothing.
Method. Read the column, then multiply the digit by the value of that column.
- Find the ten thousands column. Count the columns from the right: ones, tens, hundreds and so on.The digit is 6
- Multiply the digit by the value of its column. Each place in the ten thousands column is worth 10,000.6 × 10,000 = 60,000
- Write the value. This is the value of the digit in this number, not just the digit.60,000
Check. Check: 60,000 is 6 groups of 10,000.
Watch out. Say the value, such as 70,000, not only the digit 7.
Method. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.400,000, 50,000, 6,000, 900, 10
- Write the parts as an addition. Add the parts together to make the number.400,000 + 50,000 + 6,000 + 900 + 10
- Check by adding. Adding the parts again must give the number we started with.400,000 + 50,000 + 6,000 + 900 + 10
Check. Check: the parts add to 456,910.
Watch out. Leave out any digit that is zero. Zero adds nothing.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.825 thousand and 546
- Say the thousands. Say the number before the thousand, then the word thousand.eight hundred and twenty-five thousand
- Say the last three digits. Say them as a number up to 999.five hundred and forty-six
- Put the words together. Use a space between the two parts; use and before a number under 100.eight hundred and twenty-five thousand five hundred and forty-six
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Read the column, then multiply the digit by the value of that column.
- Find the hundred thousands column. Count the columns from the right: ones, tens, hundreds and so on.The digit is 7
- Multiply the digit by the value of its column. Each place in the hundred thousands column is worth 100,000.7 × 100,000 = 700,000
- Write the value. This is the value of the digit in this number, not just the digit.700,000
Check. Check: 700,000 is 7 groups of 100,000.
Watch out. Say the value, such as 70,000, not only the digit 7.
Method. Read the column, then multiply the digit by the value of that column.
- Find the thousands column. Count the columns from the right: ones, tens, hundreds and so on.The digit is 8
- Multiply the digit by the value of its column. Each place in the thousands column is worth 1,000.8 × 1,000 = 8,000
- Write the value. This is the value of the digit in this number, not just the digit.8,000
Check. Check: 8,000 is 8 groups of 1,000.
Watch out. Say the value, such as 70,000, not only the digit 7.
Method. Read the column, then multiply the digit by the value of that column.
- Find the thousands column. Count the columns from the right: ones, tens, hundreds and so on.The digit is 3
- Multiply the digit by the value of its column. Each place in the thousands column is worth 1,000.3 × 1,000 = 3,000
- Write the value. This is the value of the digit in this number, not just the digit.3,000
Check. Check: 3,000 is 3 groups of 1,000.
Watch out. Say the value, such as 70,000, not only the digit 7.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.798 thousand and 648
- Say the thousands. Say the number before the thousand, then the word thousand.seven hundred and ninety-eight thousand
- Say the last three digits. Say them as a number up to 999.six hundred and forty-eight
- Put the words together. Use a space between the two parts; use and before a number under 100.seven hundred and ninety-eight thousand six hundred and forty-eight
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.594 thousand and 527
- Say the thousands. Say the number before the thousand, then the word thousand.five hundred and ninety-four thousand
- Say the last three digits. Say them as a number up to 999.five hundred and twenty-seven
- Put the words together. Use a space between the two parts; use and before a number under 100.five hundred and ninety-four thousand five hundred and twenty-seven
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.500,000, 90,000, 4,000, 600, 30, 1
- Write the parts as an addition. Add the parts together to make the number.500,000 + 90,000 + 4,000 + 600 + 30 + 1
- Check by adding. Adding the parts again must give the number we started with.500,000 + 90,000 + 4,000 + 600 + 30 + 1
Check. Check: the parts add to 594,631.
Watch out. Leave out any digit that is zero. Zero adds nothing.
Method. Read the column, then multiply the digit by the value of that column.
- Find the hundred thousands column. Count the columns from the right: ones, tens, hundreds and so on.The digit is 5
- Multiply the digit by the value of its column. Each place in the hundred thousands column is worth 100,000.5 × 100,000 = 500,000
- Write the value. This is the value of the digit in this number, not just the digit.500,000
Check. Check: 500,000 is 5 groups of 100,000.
Watch out. Say the value, such as 70,000, not only the digit 7.
10,000 more or less; comparing and ordering
10,000 more than a number changes the ten thousands digit by one. 10,000 less changes it the other way.
To compare two numbers with the same number of digits, start from the left. The first column where they differ decides.
Key ideas
- Adding 10,000 changes only the ten thousands digit (carry if it is a 9).
- Compare from the left, column by column.
- Order from the smallest by comparing the digits from the left.
Method. Only the ten thousands digit changes when we add or take away 10,000.
- Look at the ten thousands digit. Adding or taking away 10,000 changes this digit by one.The ten thousands digit is 9
- Change that digit by one. Carry or borrow if the digit goes past 9 or below 0.9 + 1 = 10, so write 0 and carry 1 into the hundred thousands
- Write the answer. All the other digits stay the same.305,000
Check. Check: 305,000 take away 10,000 gives back 295,000.
Watch out. Do not change the thousands digit. 10,000 is not 1,000.
Method. Only the ten thousands digit changes when we add or take away 10,000.
- Look at the ten thousands digit. Adding or taking away 10,000 changes this digit by one.The ten thousands digit is 4
- Change that digit by one. Carry or borrow if the digit goes past 9 or below 0.4 - 1 = 3
- Write the answer. All the other digits stay the same.630,000
Check. Check: 630,000 add 10,000 gives back 640,000.
Watch out. Do not change the thousands digit. 10,000 is not 1,000.
Method. Compare the digits from the left. The first column where they differ decides.
- Compare the two numbers from the left. Look at the digits in the same column, starting with the largest.4 and 4 in the first column
- Find the first column where they differ. That column decides which number is greater.In the ten thousands column: 8 and 2
- Choose the greater number. The number with the greater digit in that column is greater.482,613
Check. Check: the other number is 428,613, which is smaller.
Watch out. Do not compare the last digits first. Start from the left.
Watch out
Watch out. 10,000 is not 1,000. Only the ten thousands digit changes, and it may carry into the hundred thousands.
Exam tip
Grown-up tip. Ask: “Which column changes?” before the child works out the answer.
Exercise 1B Practice: 10,000 more or less, and comparing
Non-calculatorMethod. Compare the digits from the left. The first column where they differ decides.
- Compare the two numbers from the left. Look at the digits in the same column, starting with the largest.2 and 3 in the first column
- Find the first column where they differ. That column decides which number is greater.In the hundred thousands column: 2 and 3
- Choose the greater number. The number with the greater digit in that column is greater.373,555
Check. Check: the other number is 239,181, which is smaller.
Watch out. Do not compare the last digits first. Start from the left.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 155,219
- Put the rest in order. Repeat: find the next smallest number.155,219 < 429,253 < 652,205 < 770,401
- Write the list. Smallest first, as the question asks.155,219, 429,253, 652,205, 770,401
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Method. Only the ten thousands digit changes when we add or take away 10,000.
- Look at the ten thousands digit. Adding or taking away 10,000 changes this digit by one.The ten thousands digit is 7
- Change that digit by one. Carry or borrow if the digit goes past 9 or below 0.7 - 1 = 6
- Write the answer. All the other digits stay the same.360,761
Check. Check: 360,761 add 10,000 gives back 370,761.
Watch out. Do not change the thousands digit. 10,000 is not 1,000.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 231,466
- Put the rest in order. Repeat: find the next smallest number.231,466 < 737,897 < 926,988 < 976,247
- Write the list. Smallest first, as the question asks.231,466, 737,897, 926,988, 976,247
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Method. Only the ten thousands digit changes when we add or take away 10,000.
- Look at the ten thousands digit. Adding or taking away 10,000 changes this digit by one.The ten thousands digit is 7
- Change that digit by one. Carry or borrow if the digit goes past 9 or below 0.7 + 1 = 8
- Write the answer. All the other digits stay the same.389,251
Check. Check: 389,251 take away 10,000 gives back 379,251.
Watch out. Do not change the thousands digit. 10,000 is not 1,000.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 159,358
- Put the rest in order. Repeat: find the next smallest number.159,358 < 278,344 < 540,497 < 961,946
- Write the list. Smallest first, as the question asks.159,358, 278,344, 540,497, 961,946
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Method. Compare the digits from the left. The first column where they differ decides.
- Compare the two numbers from the left. Look at the digits in the same column, starting with the largest.1 and 7 in the first column
- Find the first column where they differ. That column decides which number is greater.In the hundred thousands column: 1 and 7
- Choose the greater number. The number with the greater digit in that column is greater.726,162
Check. Check: the other number is 183,696, which is smaller.
Watch out. Do not compare the last digits first. Start from the left.
Method. Only the ten thousands digit changes when we add or take away 10,000.
- Look at the ten thousands digit. Adding or taking away 10,000 changes this digit by one.The ten thousands digit is 3
- Change that digit by one. Carry or borrow if the digit goes past 9 or below 0.3 + 1 = 4
- Write the answer. All the other digits stay the same.345,794
Check. Check: 345,794 take away 10,000 gives back 335,794.
Watch out. Do not change the thousands digit. 10,000 is not 1,000.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 147,407
- Put the rest in order. Repeat: find the next smallest number.147,407 < 161,173 < 714,563 < 993,272
- Write the list. Smallest first, as the question asks.147,407, 161,173, 714,563, 993,272
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Method. Only the ten thousands digit changes when we add or take away 10,000.
- Look at the ten thousands digit. Adding or taking away 10,000 changes this digit by one.The ten thousands digit is 6
- Change that digit by one. Carry or borrow if the digit goes past 9 or below 0.6 - 1 = 5
- Write the answer. All the other digits stay the same.155,825
Check. Check: 155,825 add 10,000 gives back 165,825.
Watch out. Do not change the thousands digit. 10,000 is not 1,000.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 275,739
- Put the rest in order. Repeat: find the next smallest number.275,739 < 289,999 < 341,550 < 731,589
- Write the list. Smallest first, as the question asks.275,739, 289,999, 341,550, 731,589
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Method. Only the ten thousands digit changes when we add or take away 10,000.
- Look at the ten thousands digit. Adding or taking away 10,000 changes this digit by one.The ten thousands digit is 4
- Change that digit by one. Carry or borrow if the digit goes past 9 or below 0.4 - 1 = 3
- Write the answer. All the other digits stay the same.138,018
Check. Check: 138,018 add 10,000 gives back 148,018.
Watch out. Do not change the thousands digit. 10,000 is not 1,000.
Method. Only the ten thousands digit changes when we add or take away 10,000.
- Look at the ten thousands digit. Adding or taking away 10,000 changes this digit by one.The ten thousands digit is 8
- Change that digit by one. Carry or borrow if the digit goes past 9 or below 0.8 - 1 = 7
- Write the answer. All the other digits stay the same.373,161
Check. Check: 373,161 add 10,000 gives back 383,161.
Watch out. Do not change the thousands digit. 10,000 is not 1,000.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 196,313
- Put the rest in order. Repeat: find the next smallest number.196,313 < 298,764 < 654,369 < 876,216
- Write the list. Smallest first, as the question asks.196,313, 298,764, 654,369, 876,216
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 616,936
- Put the rest in order. Repeat: find the next smallest number.616,936 < 694,987 < 842,660 < 971,828
- Write the list. Smallest first, as the question asks.616,936, 694,987, 842,660, 971,828
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 208,820
- Put the rest in order. Repeat: find the next smallest number.208,820 < 657,061 < 721,924 < 765,484
- Write the list. Smallest first, as the question asks.208,820, 657,061, 721,924, 765,484
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Rounding to the nearest 10, 100, 1000, 10000 and 100,000
To round, look at the digit just to the right of the column you are rounding to. If it is 5 or more, round up. If it is 4 or less, round down.
Then replace all the digits to the right of that column with zeros.
Key ideas
- Look one column to the right of the rounding column.
- 5 or more: round up. 4 or less: round down.
- Replace the digits after the rounding column with zeros.
Method. Look at the digit to the right of the thousands column, then decide.
- Look at the hundreds digit. This digit decides whether to round up or down.The hundreds digit is 8
- Decide: round up or down. 5 or more: round up. 4 or less: round down.8 is 5 or more, so round up
- Write the rounded number. Replace the digits after the thousands column with zeros.473,000
Check. Check: 473,000 is a multiple of 1,000 and is the closest one to 472,893.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the hundred thousands column, then decide.
- Look at the ten thousands digit. This digit decides whether to round up or down.The ten thousands digit is 7
- Decide: round up or down. 5 or more: round up. 4 or less: round down.7 is 5 or more, so round up
- Write the rounded number. Replace the digits after the hundred thousands column with zeros.500,000
Check. Check: 500,000 is a multiple of 100,000 and is the closest one to 472,893.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the ten thousands column, then decide.
- Look at the thousands digit. This digit decides whether to round up or down.The thousands digit is 6
- Decide: round up or down. 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up
- Write the rounded number. Replace the digits after the ten thousands column with zeros.300,000
Check. Check: 300,000 is a multiple of 10,000 and is the closest one to 296,458.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Watch out
Watch out. Round up only when the next digit is 5 or more. 472,893 to the nearest 1,000 is 473,000, not 472,000.
Exam tip
Grown-up tip. Ask the child to point to the digit that decides, and say “up” or “down” before writing the answer.
Exercise 1C Practice: rounding
Non-calculatorMethod. Look at the digit to the right of the hundreds column, then decide.
- Look at the tens digit. This digit decides whether to round up or down.The tens digit is 5
- Decide: round up or down. 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up
- Write the rounded number. Replace the digits after the hundreds column with zeros.394,700
Check. Check: 394,700 is a multiple of 100 and is the closest one to 394,653.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the tens column, then decide.
- Look at the ones digit. This digit decides whether to round up or down.The ones digit is 9
- Decide: round up or down. 5 or more: round up. 4 or less: round down.9 is 5 or more, so round up
- Write the rounded number. Replace the digits after the tens column with zeros.365,660
Check. Check: 365,660 is a multiple of 10 and is the closest one to 365,659.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the tens column, then decide.
- Look at the ones digit. This digit decides whether to round up or down.The ones digit is 5
- Decide: round up or down. 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up
- Write the rounded number. Replace the digits after the tens column with zeros.358,140
Check. Check: 358,140 is a multiple of 10 and is the closest one to 358,135.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the tens column, then decide.
- Look at the ones digit. This digit decides whether to round up or down.The ones digit is 5
- Decide: round up or down. 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up
- Write the rounded number. Replace the digits after the tens column with zeros.973,430
Check. Check: 973,430 is a multiple of 10 and is the closest one to 973,425.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the hundreds column, then decide.
- Look at the tens digit. This digit decides whether to round up or down.The tens digit is 8
- Decide: round up or down. 5 or more: round up. 4 or less: round down.8 is 5 or more, so round up
- Write the rounded number. Replace the digits after the hundreds column with zeros.307,700
Check. Check: 307,700 is a multiple of 100 and is the closest one to 307,682.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the tens column, then decide.
- Look at the ones digit. This digit decides whether to round up or down.The ones digit is 3
- Decide: round up or down. 5 or more: round up. 4 or less: round down.3 is 4 or less, so round down
- Write the rounded number. Replace the digits after the tens column with zeros.346,080
Check. Check: 346,080 is a multiple of 10 and is the closest one to 346,083.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the tens column, then decide.
- Look at the ones digit. This digit decides whether to round up or down.The ones digit is 9
- Decide: round up or down. 5 or more: round up. 4 or less: round down.9 is 5 or more, so round up
- Write the rounded number. Replace the digits after the tens column with zeros.357,570
Check. Check: 357,570 is a multiple of 10 and is the closest one to 357,569.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the tens column, then decide.
- Look at the ones digit. This digit decides whether to round up or down.The ones digit is 1
- Decide: round up or down. 5 or more: round up. 4 or less: round down.1 is 4 or less, so round down
- Write the rounded number. Replace the digits after the tens column with zeros.374,520
Check. Check: 374,520 is a multiple of 10 and is the closest one to 374,521.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the thousands column, then decide.
- Look at the hundreds digit. This digit decides whether to round up or down.The hundreds digit is 6
- Decide: round up or down. 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up
- Write the rounded number. Replace the digits after the thousands column with zeros.790,000
Check. Check: 790,000 is a multiple of 1,000 and is the closest one to 789,603.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the hundreds column, then decide.
- Look at the tens digit. This digit decides whether to round up or down.The tens digit is 0
- Decide: round up or down. 5 or more: round up. 4 or less: round down.0 is 4 or less, so round down
- Write the rounded number. Replace the digits after the hundreds column with zeros.435,800
Check. Check: 435,800 is a multiple of 100 and is the closest one to 435,802.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the thousands column, then decide.
- Look at the hundreds digit. This digit decides whether to round up or down.The hundreds digit is 9
- Decide: round up or down. 5 or more: round up. 4 or less: round down.9 is 5 or more, so round up
- Write the rounded number. Replace the digits after the thousands column with zeros.829,000
Check. Check: 829,000 is a multiple of 1,000 and is the closest one to 828,908.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the hundreds column, then decide.
- Look at the tens digit. This digit decides whether to round up or down.The tens digit is 8
- Decide: round up or down. 5 or more: round up. 4 or less: round down.8 is 5 or more, so round up
- Write the rounded number. Replace the digits after the hundreds column with zeros.492,000
Check. Check: 492,000 is a multiple of 100 and is the closest one to 491,985.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the ten thousands column, then decide.
- Look at the thousands digit. This digit decides whether to round up or down.The thousands digit is 2
- Decide: round up or down. 5 or more: round up. 4 or less: round down.2 is 4 or less, so round down
- Write the rounded number. Replace the digits after the ten thousands column with zeros.820,000
Check. Check: 820,000 is a multiple of 10,000 and is the closest one to 822,128.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the hundred thousands column, then decide.
- Look at the ten thousands digit. This digit decides whether to round up or down.The ten thousands digit is 6
- Decide: round up or down. 5 or more: round up. 4 or less: round down.6 is 5 or more, so round up
- Write the rounded number. Replace the digits after the hundred thousands column with zeros.200,000
Check. Check: 200,000 is a multiple of 100,000 and is the closest one to 169,143.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the hundreds column, then decide.
- Look at the tens digit. This digit decides whether to round up or down.The tens digit is 2
- Decide: round up or down. 5 or more: round up. 4 or less: round down.2 is 4 or less, so round down
- Write the rounded number. Replace the digits after the hundreds column with zeros.285,000
Check. Check: 285,000 is a multiple of 100 and is the closest one to 285,029.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Look at the digit to the right of the ten thousands column, then decide.
- Look at the thousands digit. This digit decides whether to round up or down.The thousands digit is 0
- Decide: round up or down. 5 or more: round up. 4 or less: round down.0 is 4 or less, so round down
- Write the rounded number. Replace the digits after the ten thousands column with zeros.320,000
Check. Check: 320,000 is a multiple of 10,000 and is the closest one to 320,850.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Decimals to tenths
A decimal point separates the whole number from the parts. The first digit after the point is the number of tenths.
3.4 means 3 whole ones and 4 tenths: 3 + 4/10. Between two whole numbers there are ten tenths.
Key ideas
- The first digit after the decimal point is tenths.
- A tenth is 0.1, and 4 tenths is 0.4.
- Ten tenths make one whole.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.3
- Write the tenths after a decimal point. 4/10 is 4 tenths, so the digit 4 goes after the point.3.4
- Write the answer. A decimal point separates the whole number from the tenths.3.4
Check. Check: 4/10 is 0.4, and 3 + 0.4 = 3.4.
Watch out. The tenths digit is one place after the decimal point.
Method. The first digit after the point is the number of tenths.
- Find the tenths digit. It is the first digit after the decimal point.The digit is 4
- Write its value. 4 tenths is 4/10.4/10 = 0.4
- Write the answer. The value of the digit is a decimal less than one.0.4
Check. Check: 0.4 + 3 = 3.4.
Watch out. Do not write the digit as a whole number. 4 in 3.4 is 0.4, not 4.
Method. Count the tenths from the lower whole number to the dot.
- Find the whole numbers either side. The dot is between 2 and 3.2 and 3
- Count the tenths from the lower whole number. Each small step between two whole numbers is one tenth.6 tenths after 2
- Write the decimal. Whole number first, then the point and the tenths.2.6
Check. Check: 2.6 is 6 steps past 2, and there are 10 steps to 3.
Watch out. There are ten tenths between two whole numbers. Count the small steps, not the big ones.
Watch out
Watch out. The 4 in 3.4 is worth 0.4, not 4. Read the digit after the point as tenths.
Exam tip
Grown-up tip. Use coins or a ruler marked in tenths. Ten 1p coins make 10p, which is one whole pound in tenths of pounds.
Exercise 1D Practice: tenths
Non-calculatorMethod. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.8
- Write the tenths after a decimal point. 1/10 is 1 tenths, so the digit 1 goes after the point.8.1
- Write the answer. A decimal point separates the whole number from the tenths.8.1
Check. Check: 1/10 is 0.1, and 8 + 0.1 = 8.1.
Watch out. The tenths digit is one place after the decimal point.
Method. The first digit after the point is the number of tenths.
- Find the tenths digit. It is the first digit after the decimal point.The digit is 8
- Write its value. 8 tenths is 8/10.8/10 = 0.8
- Write the answer. The value of the digit is a decimal less than one.0.8
Check. Check: 0.8 + 4 = 4.8.
Watch out. Do not write the digit as a whole number. 4 in 3.4 is 0.4, not 4.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.6
- Write the tenths after a decimal point. 1/10 is 1 tenths, so the digit 1 goes after the point.6.1
- Write the answer. A decimal point separates the whole number from the tenths.6.1
Check. Check: 1/10 is 0.1, and 6 + 0.1 = 6.1.
Watch out. The tenths digit is one place after the decimal point.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.2
- Write the tenths after a decimal point. 6/10 is 6 tenths, so the digit 6 goes after the point.2.6
- Write the answer. A decimal point separates the whole number from the tenths.2.6
Check. Check: 6/10 is 0.6, and 2 + 0.6 = 2.6.
Watch out. The tenths digit is one place after the decimal point.
Method. Count the tenths from the lower whole number to the dot.
- Find the whole numbers either side. The dot is between 3 and 4.3 and 4
- Count the tenths from the lower whole number. Each small step between two whole numbers is one tenth.4 tenths after 3
- Write the decimal. Whole number first, then the point and the tenths.3.4
Check. Check: 3.4 is 4 steps past 3, and there are 10 steps to 4.
Watch out. There are ten tenths between two whole numbers. Count the small steps, not the big ones.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.1
- Write the tenths after a decimal point. 2/10 is 2 tenths, so the digit 2 goes after the point.1.2
- Write the answer. A decimal point separates the whole number from the tenths.1.2
Check. Check: 2/10 is 0.2, and 1 + 0.2 = 1.2.
Watch out. The tenths digit is one place after the decimal point.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.9
- Write the tenths after a decimal point. 7/10 is 7 tenths, so the digit 7 goes after the point.9.7
- Write the answer. A decimal point separates the whole number from the tenths.9.7
Check. Check: 7/10 is 0.7, and 9 + 0.7 = 9.7.
Watch out. The tenths digit is one place after the decimal point.
Method. Count the tenths from the lower whole number to the dot.
- Find the whole numbers either side. The dot is between 9 and 10.9 and 10
- Count the tenths from the lower whole number. Each small step between two whole numbers is one tenth.3 tenths after 9
- Write the decimal. Whole number first, then the point and the tenths.9.3
Check. Check: 9.3 is 3 steps past 9, and there are 10 steps to 10.
Watch out. There are ten tenths between two whole numbers. Count the small steps, not the big ones.
Method. Count the tenths from the lower whole number to the dot.
- Find the whole numbers either side. The dot is between 8 and 9.8 and 9
- Count the tenths from the lower whole number. Each small step between two whole numbers is one tenth.7 tenths after 8
- Write the decimal. Whole number first, then the point and the tenths.8.7
Check. Check: 8.7 is 7 steps past 8, and there are 10 steps to 9.
Watch out. There are ten tenths between two whole numbers. Count the small steps, not the big ones.
Method. The first digit after the point is the number of tenths.
- Find the tenths digit. It is the first digit after the decimal point.The digit is 7
- Write its value. 7 tenths is 7/10.7/10 = 0.7
- Write the answer. The value of the digit is a decimal less than one.0.7
Check. Check: 0.7 + 8 = 8.7.
Watch out. Do not write the digit as a whole number. 4 in 3.4 is 0.4, not 4.
Method. The first digit after the point is the number of tenths.
- Find the tenths digit. It is the first digit after the decimal point.The digit is 2
- Write its value. 2 tenths is 2/10.2/10 = 0.2
- Write the answer. The value of the digit is a decimal less than one.0.2
Check. Check: 0.2 + 8 = 8.2.
Watch out. Do not write the digit as a whole number. 4 in 3.4 is 0.4, not 4.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.1
- Write the tenths after a decimal point. 8/10 is 8 tenths, so the digit 8 goes after the point.1.8
- Write the answer. A decimal point separates the whole number from the tenths.1.8
Check. Check: 8/10 is 0.8, and 1 + 0.8 = 1.8.
Watch out. The tenths digit is one place after the decimal point.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.6
- Write the tenths after a decimal point. 3/10 is 3 tenths, so the digit 3 goes after the point.6.3
- Write the answer. A decimal point separates the whole number from the tenths.6.3
Check. Check: 3/10 is 0.3, and 6 + 0.3 = 6.3.
Watch out. The tenths digit is one place after the decimal point.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.9
- Write the tenths after a decimal point. 9/10 is 9 tenths, so the digit 9 goes after the point.9.9
- Write the answer. A decimal point separates the whole number from the tenths.9.9
Check. Check: 9/10 is 0.9, and 9 + 0.9 = 9.9.
Watch out. The tenths digit is one place after the decimal point.
Method. The first digit after the point is the number of tenths.
- Find the tenths digit. It is the first digit after the decimal point.The digit is 5
- Write its value. 5 tenths is 5/10.5/10 = 0.5
- Write the answer. The value of the digit is a decimal less than one.0.5
Check. Check: 0.5 + 4 = 4.5.
Watch out. Do not write the digit as a whole number. 4 in 3.4 is 0.4, not 4.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.2
- Write the tenths after a decimal point. 8/10 is 8 tenths, so the digit 8 goes after the point.2.8
- Write the answer. A decimal point separates the whole number from the tenths.2.8
Check. Check: 8/10 is 0.8, and 2 + 0.8 = 2.8.
Watch out. The tenths digit is one place after the decimal point.
Comparing and ordering decimals to tenths
Compare the whole numbers first. If they are the same, compare the tenths digits.
The number with more tenths is the greater one, even if it has fewer digits after the point.
Key ideas
- Compare the whole numbers first.
- If the whole numbers match, compare the tenths.
- Write the list in order from the smallest.
Method. Compare the whole numbers, then the tenths.
- Compare the whole numbers first. The bigger whole number is the bigger decimal.3 and 3
- If the whole numbers are the same, compare the tenths. The tenths digit decides when the whole numbers match.7 and 4 tenths
- Choose the greater decimal. This is the decimal with more of the bigger part.3.7
Check. Check: 3.7 is 37 tenths, and 3.4 is 34 tenths.
Watch out. 3.7 is greater than 3.4, not smaller. Compare the tenths: 7 tenths is more than 4 tenths.
Method. Compare the whole numbers first, then the tenths.
- Compare the whole numbers. Put the numbers with the smallest whole number first.4, 3, 4, 3
- Compare the tenths when the whole numbers match. Use the tenths digit to break a tie.4.2, 3.9, 4.1, 3.6
- Write the list smallest first. Read the order from the smallest to the largest.3.6, 3.9, 4.1, 4.2
Check. Check: the first number is the smallest and the last is the greatest.
Watch out. Do not order by the number of digits after the point. 4.2 is greater than 3.9.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.3.2 = 32 tenths and 3.5 = 35 tenths
- Find the tenths in between. Any number of tenths strictly between them works.3.3 or 3.4
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 3.3 or 3.4
Check. Check: each choice is greater than 3.2 and less than 3.5.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Watch out
Watch out. 3.7 is greater than 3.4. Do not think that 4 is bigger than 7 because the number is smaller.
Exam tip
Grown-up tip. Ask: “Which is bigger, 4.2 or 3.9? How do you know?” The whole number decides first.
Exercise 1E Practice: comparing and ordering tenths
Non-calculatorMethod. Compare the whole numbers, then the tenths.
- Compare the whole numbers first. The bigger whole number is the bigger decimal.9 and 2
- If the whole numbers are the same, compare the tenths. The tenths digit decides when the whole numbers match.3 and 9 tenths
- Choose the greater decimal. This is the decimal with more of the bigger part.9.3
Check. Check: 9.3 is 93 tenths, and 2.9 is 29 tenths.
Watch out. 3.7 is greater than 3.4, not smaller. Compare the tenths: 7 tenths is more than 4 tenths.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.8.5 = 85 tenths and 8.8 = 88 tenths
- Find the tenths in between. Any number of tenths strictly between them works.8.6 or 8.7
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 8.6 or 8.7
Check. Check: each choice is greater than 8.5 and less than 8.8.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Compare the whole numbers first, then the tenths.
- Compare the whole numbers. Put the numbers with the smallest whole number first.2, 2, 3, 2
- Compare the tenths when the whole numbers match. Use the tenths digit to break a tie.2.7, 2.1, 3.4, 2.4
- Write the list smallest first. Read the order from the smallest to the largest.2.1, 2.4, 2.7, 3.4
Check. Check: the first number is the smallest and the last is the greatest.
Watch out. Do not order by the number of digits after the point. 4.2 is greater than 3.9.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.4.2 = 42 tenths and 4.7 = 47 tenths
- Find the tenths in between. Any number of tenths strictly between them works.4.3 or 4.4 or 4.5 or 4.6
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 4.3, 4.4, 4.5 or 4.6
Check. Check: each choice is greater than 4.2 and less than 4.7.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Compare the whole numbers first, then the tenths.
- Compare the whole numbers. Put the numbers with the smallest whole number first.2, 4, 4, 1
- Compare the tenths when the whole numbers match. Use the tenths digit to break a tie.2.0, 4.3, 4.1, 1.1
- Write the list smallest first. Read the order from the smallest to the largest.1.1, 2.0, 4.1, 4.3
Check. Check: the first number is the smallest and the last is the greatest.
Watch out. Do not order by the number of digits after the point. 4.2 is greater than 3.9.
Method. Compare the whole numbers, then the tenths.
- Compare the whole numbers first. The bigger whole number is the bigger decimal.9 and 2
- If the whole numbers are the same, compare the tenths. The tenths digit decides when the whole numbers match.7 and 3 tenths
- Choose the greater decimal. This is the decimal with more of the bigger part.9.7
Check. Check: 9.7 is 97 tenths, and 2.3 is 23 tenths.
Watch out. 3.7 is greater than 3.4, not smaller. Compare the tenths: 7 tenths is more than 4 tenths.
Method. Compare the whole numbers first, then the tenths.
- Compare the whole numbers. Put the numbers with the smallest whole number first.1, 5, 1, 5
- Compare the tenths when the whole numbers match. Use the tenths digit to break a tie.1.5, 5.4, 1.9, 5.3
- Write the list smallest first. Read the order from the smallest to the largest.1.5, 1.9, 5.3, 5.4
Check. Check: the first number is the smallest and the last is the greatest.
Watch out. Do not order by the number of digits after the point. 4.2 is greater than 3.9.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.1.5 = 15 tenths and 2.1 = 21 tenths
- Find the tenths in between. Any number of tenths strictly between them works.1.6 or 1.7 or 1.8 or 1.9 or 2.0
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 1.6, 1.7, 1.8, 1.9 or 2.0
Check. Check: each choice is greater than 1.5 and less than 2.1.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.1.2 = 12 tenths and 1.4 = 14 tenths
- Find the tenths in between. Any number of tenths strictly between them works.1.3
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 1.3
Check. Check: each choice is greater than 1.2 and less than 1.4.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Compare the whole numbers, then the tenths.
- Compare the whole numbers first. The bigger whole number is the bigger decimal.1 and 4
- If the whole numbers are the same, compare the tenths. The tenths digit decides when the whole numbers match.1 and 4 tenths
- Choose the greater decimal. This is the decimal with more of the bigger part.4.4
Check. Check: 4.4 is 44 tenths, and 1.1 is 11 tenths.
Watch out. 3.7 is greater than 3.4, not smaller. Compare the tenths: 7 tenths is more than 4 tenths.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.4.9 = 49 tenths and 5.2 = 52 tenths
- Find the tenths in between. Any number of tenths strictly between them works.5.0 or 5.1
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 5.0 or 5.1
Check. Check: each choice is greater than 4.9 and less than 5.2.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.4.5 = 45 tenths and 4.7 = 47 tenths
- Find the tenths in between. Any number of tenths strictly between them works.4.6
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 4.6
Check. Check: each choice is greater than 4.5 and less than 4.7.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Compare the whole numbers first, then the tenths.
- Compare the whole numbers. Put the numbers with the smallest whole number first.5, 4, 7, 8
- Compare the tenths when the whole numbers match. Use the tenths digit to break a tie.5.2, 4.8, 7.5, 8.6
- Write the list smallest first. Read the order from the smallest to the largest.4.8, 5.2, 7.5, 8.6
Check. Check: the first number is the smallest and the last is the greatest.
Watch out. Do not order by the number of digits after the point. 4.2 is greater than 3.9.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.4.5 = 45 tenths and 4.8 = 48 tenths
- Find the tenths in between. Any number of tenths strictly between them works.4.6 or 4.7
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 4.6 or 4.7
Check. Check: each choice is greater than 4.5 and less than 4.8.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.7.0 = 70 tenths and 7.4 = 74 tenths
- Find the tenths in between. Any number of tenths strictly between them works.7.1 or 7.2 or 7.3
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 7.1, 7.2 or 7.3
Check. Check: each choice is greater than 7.0 and less than 7.4.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Compare the whole numbers first, then the tenths.
- Compare the whole numbers. Put the numbers with the smallest whole number first.3, 3, 1, 1
- Compare the tenths when the whole numbers match. Use the tenths digit to break a tie.3.9, 3.8, 1.8, 1.2
- Write the list smallest first. Read the order from the smallest to the largest.1.2, 1.8, 3.8, 3.9
Check. Check: the first number is the smallest and the last is the greatest.
Watch out. Do not order by the number of digits after the point. 4.2 is greater than 3.9.
Chapter summary
| Skill | Method |
|---|---|
| Value of a digit | Name the column, then digit × column value |
| Big numbers in words | Say the thousands, then the rest; use and before tens and ones |
| 10,000 more or less | Change the ten thousands digit by one; carry or borrow if needed |
| Rounding | Look one column to the right: 5 or more round up; then zeros |
| Tenths | The digit after the point is the tenths; 3.4 = 3 + 4/10 |
| Comparing decimals | Whole numbers first, then tenths |
Can you…?
- I can say the value of each digit in a number to 1,000,000
- I can read and write big numbers in numerals and words
- I can find 10,000 more and 10,000 less than a number
- I can round to the nearest 10, 100, 1000, 10000 and 100,000
- I can write and place decimals to tenths on a number line
- I can compare and order decimals to tenths
Key terms
- column
- a place in a number, such as hundreds or tens
- partition
- split a number into the value of each digit
- round
- make a number simpler, by counting to the nearest 10, 100 and so on
- tenths
- parts when a whole is split into ten equal parts
- decimal point
- the dot that separates the whole number from the tenths
Exercise 1Z Check-up
Non-calculatorMethod. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.3.7 = 37 tenths and 3.9 = 39 tenths
- Find the tenths in between. Any number of tenths strictly between them works.3.8
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 3.8
Check. Check: each choice is greater than 3.7 and less than 3.9.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Compare the numbers from the left, and write them smallest first.
- Find the smallest number. Compare the digits from the left.Smallest: 145,974
- Put the rest in order. Repeat: find the next smallest number.145,974 < 319,401 < 338,787 < 516,230
- Write the list. Smallest first, as the question asks.145,974, 319,401, 338,787, 516,230
Check. Check: the first number is the smallest and the last is the largest.
Watch out. A number with more digits is greater; with the same number of digits, compare from the left.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.537 thousand and 447
- Say the thousands. Say the number before the thousand, then the word thousand.five hundred and thirty-seven thousand
- Say the last three digits. Say them as a number up to 999.four hundred and forty-seven
- Put the words together. Use a space between the two parts; use and before a number under 100.five hundred and thirty-seven thousand four hundred and forty-seven
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Read the column, then multiply the digit by the value of that column.
- Find the thousands column. Count the columns from the right: ones, tens, hundreds and so on.The digit is 8
- Multiply the digit by the value of its column. Each place in the thousands column is worth 1,000.8 × 1,000 = 8,000
- Write the value. This is the value of the digit in this number, not just the digit.8,000
Check. Check: 8,000 is 8 groups of 1,000.
Watch out. Say the value, such as 70,000, not only the digit 7.
Method. Turn both numbers into tenths, then choose any tenths number between them.
- Write both numbers in tenths. Count how many tenths each number has.1.4 = 14 tenths and 1.6 = 16 tenths
- Find the tenths in between. Any number of tenths strictly between them works.1.5
- Write an answer. Each is between the two numbers, so each is correct.Accept any of 1.5
Check. Check: each choice is greater than 1.4 and less than 1.6.
Watch out. Do not choose the same number as one of the two numbers in the question. It must be strictly between.
Method. Look at the digit to the right of the tens column, then decide.
- Look at the ones digit. This digit decides whether to round up or down.The ones digit is 7
- Decide: round up or down. 5 or more: round up. 4 or less: round down.7 is 5 or more, so round up
- Write the rounded number. Replace the digits after the tens column with zeros.820,240
Check. Check: 820,240 is a multiple of 10 and is the closest one to 820,237.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.900,000, 20,000, 2,000, 80, 4
- Write the parts as an addition. Add the parts together to make the number.900,000 + 20,000 + 2,000 + 80 + 4
- Check by adding. Adding the parts again must give the number we started with.900,000 + 20,000 + 2,000 + 80 + 4
Check. Check: the parts add to 922,084.
Watch out. Leave out any digit that is zero. Zero adds nothing.
Method. Compare the whole numbers first, then the tenths.
- Compare the whole numbers. Put the numbers with the smallest whole number first.5, 6, 5, 9
- Compare the tenths when the whole numbers match. Use the tenths digit to break a tie.5.0, 6.8, 5.5, 9.3
- Write the list smallest first. Read the order from the smallest to the largest.5.0, 5.5, 6.8, 9.3
Check. Check: the first number is the smallest and the last is the greatest.
Watch out. Do not order by the number of digits after the point. 4.2 is greater than 3.9.
Method. Compare the whole numbers, then the tenths.
- Compare the whole numbers first. The bigger whole number is the bigger decimal.8 and 7
- If the whole numbers are the same, compare the tenths. The tenths digit decides when the whole numbers match.0 and 4 tenths
- Choose the greater decimal. This is the decimal with more of the bigger part.8.0
Check. Check: 8.0 is 80 tenths, and 7.4 is 74 tenths.
Watch out. 3.7 is greater than 3.4, not smaller. Compare the tenths: 7 tenths is more than 4 tenths.
Method. Look at the digit to the right of the thousands column, then decide.
- Look at the hundreds digit. This digit decides whether to round up or down.The hundreds digit is 0
- Decide: round up or down. 5 or more: round up. 4 or less: round down.0 is 4 or less, so round down
- Write the rounded number. Replace the digits after the thousands column with zeros.285,000
Check. Check: 285,000 is a multiple of 1,000 and is the closest one to 285,067.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Total 19 marks. Allow about 19 minutes.
Exercise 1X Practice test questions
Non-calculatorMethod. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.8
- Write the tenths after a decimal point. 5/10 is 5 tenths, so the digit 5 goes after the point.8.5
- Write the answer. A decimal point separates the whole number from the tenths.8.5
Check. Check: 5/10 is 0.5, and 8 + 0.5 = 8.5.
Watch out. The tenths digit is one place after the decimal point.
Method. Look at the digit to the right of the tens column, then decide.
- Look at the ones digit. This digit decides whether to round up or down.The ones digit is 3
- Decide: round up or down. 5 or more: round up. 4 or less: round down.3 is 4 or less, so round down
- Write the rounded number. Replace the digits after the tens column with zeros.664,610
Check. Check: 664,610 is a multiple of 10 and is the closest one to 664,613.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Read the thousands, then the last three digits, and join them with the word thousand.
- Split the number into thousands and the last three digits. Read the thousands first, then the rest.583 thousand and 904
- Say the thousands. Say the number before the thousand, then the word thousand.five hundred and eighty-three thousand
- Say the last three digits. Say them as a number up to 999.nine hundred and four
- Put the words together. Use a space between the two parts; use and before a number under 100.five hundred and eighty-three thousand nine hundred and four
Check. Check: count the words so that each part matches its digits.
Watch out. Do not write the digits in words one by one. Say the parts. Use and before the tens and ones.
Method. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.600,000, 80,000, 2,000, 700, 10, 9
- Write the parts as an addition. Add the parts together to make the number.600,000 + 80,000 + 2,000 + 700 + 10 + 9
- Check by adding. Adding the parts again must give the number we started with.600,000 + 80,000 + 2,000 + 700 + 10 + 9
Check. Check: the parts add to 682,719.
Watch out. Leave out any digit that is zero. Zero adds nothing.
Method. Look at the digit to the right of the ten thousands column, then decide.
- Look at the thousands digit. This digit decides whether to round up or down.The thousands digit is 5
- Decide: round up or down. 5 or more: round up. 4 or less: round down.5 is 5 or more, so round up
- Write the rounded number. Replace the digits after the ten thousands column with zeros.270,000
Check. Check: 270,000 is a multiple of 10,000 and is the closest one to 265,571.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.200,000, 30,000, 5,000, 300, 50, 8
- Write the parts as an addition. Add the parts together to make the number.200,000 + 30,000 + 5,000 + 300 + 50 + 8
- Check by adding. Adding the parts again must give the number we started with.200,000 + 30,000 + 5,000 + 300 + 50 + 8
Check. Check: the parts add to 235,358.
Watch out. Leave out any digit that is zero. Zero adds nothing.
Method. Look at the digit to the right of the thousands column, then decide.
- Look at the hundreds digit. This digit decides whether to round up or down.The hundreds digit is 3
- Decide: round up or down. 5 or more: round up. 4 or less: round down.3 is 4 or less, so round down
- Write the rounded number. Replace the digits after the thousands column with zeros.282,000
Check. Check: 282,000 is a multiple of 1,000 and is the closest one to 282,376.
Watch out. Round up only when the next digit is 5 or more. Do not round up on a 4.
Method. Compare the digits from the left. The first column where they differ decides.
- Compare the two numbers from the left. Look at the digits in the same column, starting with the largest.2 and 5 in the first column
- Find the first column where they differ. That column decides which number is greater.In the hundred thousands column: 2 and 5
- Choose the greater number. The number with the greater digit in that column is greater.567,810
Check. Check: the other number is 216,103, which is smaller.
Watch out. Do not compare the last digits first. Start from the left.
Method. Write the whole number, then a decimal point, then the tenths digit.
- Write the whole number first. This is the part before the decimal point.2
- Write the tenths after a decimal point. 9/10 is 9 tenths, so the digit 9 goes after the point.2.9
- Write the answer. A decimal point separates the whole number from the tenths.2.9
Check. Check: 9/10 is 0.9, and 2 + 0.9 = 2.9.
Watch out. The tenths digit is one place after the decimal point.
Method. Partition the number into the value of each digit.
- Find the value of each digit. Multiply each digit by the value of its column; leave out zeros.700,000, 60,000, 8,000, 800, 50, 5
- Write the parts as an addition. Add the parts together to make the number.700,000 + 60,000 + 8,000 + 800 + 50 + 5
- Check by adding. Adding the parts again must give the number we started with.700,000 + 60,000 + 8,000 + 800 + 50 + 5
Check. Check: the parts add to 768,855.
Watch out. Leave out any digit that is zero. Zero adds nothing.