Tens and ones
By the end of this chapter you will be able to
- Know that ten ones make one ten
- Say how many tens and ones are in a number
- Read and write numbers from 0 to 20 in words
- Make a number from tens and ones
You should already know
- Counting to 20 (Level 1)
- Counting to 100 (Level 2, Chapter 1)
Where this leads
- Comparing and ordering to 100 (Chapter 3)
- Adding and subtracting within 100 (Chapter 7)
Step-by-step practice: maths (Level 2). Small steps, repeated until fluent. Content: Know that 10 ones make one ten, and that a ten is a group of ten, Split a 2-digit number into tens and ones using a place value grid or ten frames, Read and write numbers from 0 to 20 in words, Say how many tens and how many ones are in a number up to 100, Build a number from a given number of tens and ones.
Exercise P Do you remember?
Non-calculatorMethod. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.2 tens
- Look at the second digit. It is the number of ones.3 ones
- Write the answer. Say the tens, then the ones.2 tens and 3 ones
Check. 2 tens is 20, and 20 + 3 = 23.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.9
- Say its name. Each number from 0 to 20 has its own name.nine
- Write the answer. nine
Check. Count to 9 and stop on nine.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.sixteen
- Find the numeral. sixteen is the number 16.sixteen = 16
- Write the numeral. 16
Check. Count to 16 and check you say sixteen at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.2 tens
- Count the ones in each ten. Ten ones in every ten.2 x 10 = 20
- Write the answer. That is the total number of ones.20
Check. Count in tens to check: 10, 20.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.4 tens = 40
- Add the ones. The ones are added on to the tens.40 + 7 = 47
- Write the number. 47
Check. Split 47 back into tens and ones: 4 tens and 7 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Ten ones make one ten
A ten is a group of ten ones. A full ten frame has ten counters, so it shows one ten.
If you have three groups of ten, you have three tens, and that is thirty ones.
Key ideas
- A ten is a group of ten ones.
- Two tens are twenty ones.
- Count in tens: 10, 20, 30 ...
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.3 tens
- Count the ones in each ten. Ten ones in every ten.3 x 10 = 30
- Write the answer. That is the total number of ones.30
Check. Count in tens to check: 10, 20, 30.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.5 tens
- Count the ones in each ten. Ten ones in every ten.5 x 10 = 50
- Write the answer. That is the total number of ones.50
Check. Count in tens to check: 10, 20, 30, 40, 50.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.8 tens
- Count the ones in each ten. Ten ones in every ten.8 x 10 = 80
- Write the answer. That is the total number of ones.80
Check. Count in tens to check: 10, 20, 30, 40, 50, 60, 70, 80.
Watch out. A ten is ten ones. Do not count the tens as ones.
Watch out
Watch out. Three tens are not three ones. Three tens is thirty ones.
Exam tip
Grown-up tip. Use ten cubes or ten buttons. Make a ten in a cup, then count the cups.
Exercise 2A Practice: tens and ones
Non-calculatorMethod. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.4 tens
- Count the ones in each ten. Ten ones in every ten.4 x 10 = 40
- Write the answer. That is the total number of ones.40
Check. Count in tens to check: 10, 20, 30, 40.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.7 tens
- Count the ones in each ten. Ten ones in every ten.7 x 10 = 70
- Write the answer. That is the total number of ones.70
Check. Count in tens to check: 10, 20, 30, 40, 50, 60, 70.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.9 tens
- Count the ones in each ten. Ten ones in every ten.9 x 10 = 90
- Write the answer. That is the total number of ones.90
Check. Count in tens to check: 10, 20, 30, 40, 50, 60, 70, 80, 90.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.2 tens
- Count the ones in each ten. Ten ones in every ten.2 x 10 = 20
- Write the answer. That is the total number of ones.20
Check. Count in tens to check: 10, 20.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.5 tens
- Count the ones in each ten. Ten ones in every ten.5 x 10 = 50
- Write the answer. That is the total number of ones.50
Check. Count in tens to check: 10, 20, 30, 40, 50.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.8 tens
- Count the ones in each ten. Ten ones in every ten.8 x 10 = 80
- Write the answer. That is the total number of ones.80
Check. Count in tens to check: 10, 20, 30, 40, 50, 60, 70, 80.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.1 ten
- Count the ones in each ten. Ten ones in every ten.1 x 10 = 10
- Write the answer. That is the total number of ones.10
Check. Count in tens to check: 10.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.3 tens
- Count the ones in each ten. Ten ones in every ten.3 x 10 = 30
- Write the answer. That is the total number of ones.30
Check. Count in tens to check: 10, 20, 30.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Count the ones in the tens.
- Look at the tens. Each ten has ten ones.4 tens
- Count the ones. Four tens is ten ones four times.4 x 10 = 40
- Compare with Sam. Sam has 40 ones, not 4 ones.No, 40 ones
Check. Count in tens: 10, 20, 30, 40.
Watch out. A ten is ten ones, so 4 tens is 40 ones.
Tens and ones in a number
Every 2-digit number has a tens digit and a ones digit.
In 47, the 4 means 4 tens, which is 40. The 7 means 7 ones.
Key ideas
- The left digit is the tens.
- The right digit is the ones.
- 47 is 4 tens and 7 ones.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.4 tens
- Look at the second digit. It is the number of ones.7 ones
- Write the answer. Say the tens, then the ones.4 tens and 7 ones
Check. 4 tens is 40, and 40 + 7 = 47.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.9 tens
- Look at the second digit. It is the number of ones.0 ones
- Write the answer. Say the tens, then the ones.9 tens and 0 ones
Check. 9 tens is 90, and 90 + 0 = 90.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.6 tens
- Look at the second digit. It is the number of ones.2 ones
- Write the answer. Say the tens, then the ones.6 tens and 2 ones
Check. 6 tens is 60, and 60 + 2 = 62.
Watch out. Read the digits from left to right. The left digit is the tens.
Watch out
Watch out. In 47 the 4 is worth 40, not 4. Position matters.
Exam tip
Grown-up tip. Write numbers on a place value grid with columns for tens and ones. Ask: “How many tens?” first.
Exercise 2B Practice: tens and ones in a number
Non-calculatorMethod. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.1 tens
- Look at the second digit. It is the number of ones.2 ones
- Write the answer. Say the tens, then the ones.1 tens and 2 ones
Check. 1 tens is 10, and 10 + 2 = 12.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.5 tens
- Look at the second digit. It is the number of ones.9 ones
- Write the answer. Say the tens, then the ones.5 tens and 9 ones
Check. 5 tens is 50, and 50 + 9 = 59.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.6 tens
- Look at the second digit. It is the number of ones.9 ones
- Write the answer. Say the tens, then the ones.6 tens and 9 ones
Check. 6 tens is 60, and 60 + 9 = 69.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.5 tens
- Look at the second digit. It is the number of ones.6 ones
- Write the answer. Say the tens, then the ones.5 tens and 6 ones
Check. 5 tens is 50, and 50 + 6 = 56.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.7 tens
- Look at the second digit. It is the number of ones.4 ones
- Write the answer. Say the tens, then the ones.7 tens and 4 ones
Check. 7 tens is 70, and 70 + 4 = 74.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.9 tens
- Look at the second digit. It is the number of ones.4 ones
- Write the answer. Say the tens, then the ones.9 tens and 4 ones
Check. 9 tens is 90, and 90 + 4 = 94.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.1 tens
- Look at the second digit. It is the number of ones.5 ones
- Write the answer. Say the tens, then the ones.1 tens and 5 ones
Check. 1 tens is 10, and 10 + 5 = 15.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.9 tens
- Look at the second digit. It is the number of ones.7 ones
- Write the answer. Say the tens, then the ones.9 tens and 7 ones
Check. 9 tens is 90, and 90 + 7 = 97.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.7 tens
- Look at the second digit. It is the number of ones.0 ones
- Write the answer. Say the tens, then the ones.7 tens and 0 ones
Check. 7 tens is 70, and 70 + 0 = 70.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.4 tens
- Look at the second digit. It is the number of ones.7 ones
- Write the answer. Say the tens, then the ones.4 tens and 7 ones
Check. 4 tens is 40, and 40 + 7 = 47.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.9 tens
- Look at the second digit. It is the number of ones.9 ones
- Write the answer. Say the tens, then the ones.9 tens and 9 ones
Check. 9 tens is 90, and 90 + 9 = 99.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.8 tens
- Look at the second digit. It is the number of ones.5 ones
- Write the answer. Say the tens, then the ones.8 tens and 5 ones
Check. 8 tens is 80, and 80 + 5 = 85.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.8 tens
- Look at the second digit. It is the number of ones.2 ones
- Write the answer. Say the tens, then the ones.8 tens and 2 ones
Check. 8 tens is 80, and 80 + 2 = 82.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.2 tens
- Look at the second digit. It is the number of ones.3 ones
- Write the answer. Say the tens, then the ones.2 tens and 3 ones
Check. 2 tens is 20, and 20 + 3 = 23.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.1 tens
- Look at the second digit. It is the number of ones.8 ones
- Write the answer. Say the tens, then the ones.1 tens and 8 ones
Check. 1 tens is 10, and 10 + 8 = 18.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.7 tens
- Look at the second digit. It is the number of ones.1 ones
- Write the answer. Say the tens, then the ones.7 tens and 1 ones
Check. 7 tens is 70, and 70 + 1 = 71.
Watch out. Read the digits from left to right. The left digit is the tens.
Numbers 0 to 20 in words
Every number from 0 to 20 has its own name. Some names are hard to spell, so say them slowly.
The teen numbers 13 to 19 end in -teen. Each one is ten plus some ones.
Key ideas
- Zero to twenty each have a name.
- Thirteen, fourteen ... nineteen end in -teen.
- Twenty is 2 tens.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.13
- Say its name. Each number from 0 to 20 has its own name.thirteen
- Write the answer. thirteen
Check. Count to 13 and stop on thirteen.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.nineteen
- Find the numeral. nineteen is the number 19.nineteen = 19
- Write the numeral. 19
Check. Count to 19 and check you say nineteen at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.7
- Say its name. Each number from 0 to 20 has its own name.seven
- Write the answer. seven
Check. Count to 7 and stop on seven.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Watch out
Watch out. Fifteen has a letter f, not a v. Count to check the spelling.
Exam tip
Grown-up tip. Write the words on cards and match each card to its numeral. Say the names together.
Exercise 2C Practice: numbers in words
Non-calculatorMethod. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.19
- Say its name. Each number from 0 to 20 has its own name.nineteen
- Write the answer. nineteen
Check. Count to 19 and stop on nineteen.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.sixteen
- Find the numeral. sixteen is the number 16.sixteen = 16
- Write the numeral. 16
Check. Count to 16 and check you say sixteen at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.5
- Say its name. Each number from 0 to 20 has its own name.five
- Write the answer. five
Check. Count to 5 and stop on five.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.two
- Find the numeral. two is the number 2.two = 2
- Write the numeral. 2
Check. Count to 2 and check you say two at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.3
- Say its name. Each number from 0 to 20 has its own name.three
- Write the answer. three
Check. Count to 3 and stop on three.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.twelve
- Find the numeral. twelve is the number 12.twelve = 12
- Write the numeral. 12
Check. Count to 12 and check you say twelve at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.20
- Say its name. Each number from 0 to 20 has its own name.twenty
- Write the answer. twenty
Check. Count to 20 and stop on twenty.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.four
- Find the numeral. four is the number 4.four = 4
- Write the numeral. 4
Check. Count to 4 and check you say four at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.0
- Say its name. Each number from 0 to 20 has its own name.zero
- Write the answer. zero
Check. Count to 0 and stop on zero.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.one
- Find the numeral. one is the number 1.one = 1
- Write the numeral. 1
Check. Count to 1 and check you say one at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.8
- Say its name. Each number from 0 to 20 has its own name.eight
- Write the answer. eight
Check. Count to 8 and stop on eight.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.ten
- Find the numeral. ten is the number 10.ten = 10
- Write the numeral. 10
Check. Count to 10 and check you say ten at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.11
- Say its name. Each number from 0 to 20 has its own name.eleven
- Write the answer. eleven
Check. Count to 11 and stop on eleven.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.eighteen
- Find the numeral. eighteen is the number 18.eighteen = 18
- Write the numeral. 18
Check. Count to 18 and check you say eighteen at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.15
- Say its name. Each number from 0 to 20 has its own name.fifteen
- Write the answer. fifteen
Check. Count to 15 and stop on fifteen.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.thirteen
- Find the numeral. thirteen is the number 13.thirteen = 13
- Write the numeral. 13
Check. Count to 13 and check you say thirteen at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Building numbers from tens and ones
To build a number, start with the tens and then add the ones.
For example, 5 tens and 2 ones make 52. Write the tens digit first.
Key ideas
- Tens first, then ones.
- The tens digit goes on the left.
- Check by splitting the number again.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.5 tens = 50
- Add the ones. The ones are added on to the tens.50 + 2 = 52
- Write the number. 52
Check. Split 52 back into tens and ones: 5 tens and 2 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.8 tens = 80
- Add the ones. The ones are added on to the tens.80 + 0 = 80
- Write the number. 80
Check. Split 80 back into tens and ones: 8 tens and 0 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Change the tens word to tens, then add the ones.
- Change the tens word. sixty is 6 tens.6 tens = 60
- Add the ones. Put the ones on the end.60 + 9 = 69
- Write the answer. 69
Check. 69 has 6 tens and 9 ones.
Watch out. Ask yourself: how many tens are in the number?
Watch out
Watch out. 3 tens and 5 ones is 35. It is not 8, and it is not 53.
Exam tip
Grown-up tip. Make numbers with tens sticks and single cubes. Ask: “How many tens, how many ones?”
Exercise 2D Practice: making numbers
Non-calculatorMethod. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.1 tens = 10
- Add the ones. The ones are added on to the tens.10 + 3 = 13
- Write the number. 13
Check. Split 13 back into tens and ones: 1 tens and 3 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.7 tens = 70
- Add the ones. The ones are added on to the tens.70 + 6 = 76
- Write the number. 76
Check. Split 76 back into tens and ones: 7 tens and 6 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.5 tens = 50
- Add the ones. The ones are added on to the tens.50 + 4 = 54
- Write the number. 54
Check. Split 54 back into tens and ones: 5 tens and 4 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Change the tens word to tens, then add the ones.
- Change the tens word. seventy is 7 tens.7 tens = 70
- Add the ones. Put the ones on the end.70 + 1 = 71
- Write the answer. 71
Check. 71 has 7 tens and 1 ones.
Watch out. Ask yourself: how many tens are in the number?
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.4 tens = 40
- Add the ones. The ones are added on to the tens.40 + 4 = 44
- Write the number. 44
Check. Split 44 back into tens and ones: 4 tens and 4 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.5 tens = 50
- Add the ones. The ones are added on to the tens.50 + 7 = 57
- Write the number. 57
Check. Split 57 back into tens and ones: 5 tens and 7 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.8 tens = 80
- Add the ones. The ones are added on to the tens.80 + 7 = 87
- Write the number. 87
Check. Split 87 back into tens and ones: 8 tens and 7 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.6 tens = 60
- Add the ones. The ones are added on to the tens.60 + 6 = 66
- Write the number. 66
Check. Split 66 back into tens and ones: 6 tens and 6 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.8 tens = 80
- Add the ones. The ones are added on to the tens.80 + 6 = 86
- Write the number. 86
Check. Split 86 back into tens and ones: 8 tens and 6 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Change the tens word to tens, then add the ones.
- Change the tens word. ten is 1 tens.1 tens = 10
- Add the ones. Put the ones on the end.10 + 3 = 13
- Write the answer. 13
Check. 13 has 1 tens and 3 ones.
Watch out. Ask yourself: how many tens are in the number?
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.3 tens = 30
- Add the ones. The ones are added on to the tens.30 + 5 = 35
- Write the number. 35
Check. Split 35 back into tens and ones: 3 tens and 5 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.7 tens = 70
- Add the ones. The ones are added on to the tens.70 + 7 = 77
- Write the number. 77
Check. Split 77 back into tens and ones: 7 tens and 7 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Change the tens word to tens, then add the ones.
- Change the tens word. seventy is 7 tens.7 tens = 70
- Add the ones. Put the ones on the end.70 + 8 = 78
- Write the answer. 78
Check. 78 has 7 tens and 8 ones.
Watch out. Ask yourself: how many tens are in the number?
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.6 tens = 60
- Add the ones. The ones are added on to the tens.60 + 3 = 63
- Write the number. 63
Check. Split 63 back into tens and ones: 6 tens and 3 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.8 tens = 80
- Add the ones. The ones are added on to the tens.80 + 3 = 83
- Write the number. 83
Check. Split 83 back into tens and ones: 8 tens and 3 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Change the tens word to tens, then add the ones.
- Change the tens word. ten is 1 tens.1 tens = 10
- Add the ones. Put the ones on the end.10 + 1 = 11
- Write the answer. 11
Check. 11 has 1 tens and 1 ones.
Watch out. Ask yourself: how many tens are in the number?
Chapter summary
| Skill | Method |
|---|---|
| Ten ones | A ten is ten ones. Count the tens, then multiply by ten |
| Tens and ones | The left digit is the tens; the right digit is the ones |
| Words 0 to 20 | Say each name, then write it or read it |
| Building numbers | Put the tens first, then add the ones |
Can you…?
- I know that ten ones make one ten
- I can say how many tens and ones are in a 2-digit number
- I can read and write numbers from 0 to 20 in words
- I can build a number from tens and ones
Key terms
- ten
- a group of ten ones
- tens digit
- the digit that shows how many tens, for example the 4 in 47
- ones digit
- the digit that shows how many ones, for example the 7 in 47
- place value
- the value a digit has because of where it is in the number
Exercise 2Z Check-up
Non-calculatorMethod. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.1 ten
- Count the ones in each ten. Ten ones in every ten.1 x 10 = 10
- Write the answer. That is the total number of ones.10
Check. Count in tens to check: 10.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.twenty
- Find the numeral. twenty is the number 20.twenty = 20
- Write the numeral. 20
Check. Count to 20 and check you say twenty at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.9 tens
- Count the ones in each ten. Ten ones in every ten.9 x 10 = 90
- Write the answer. That is the total number of ones.90
Check. Count in tens to check: 10, 20, 30, 40, 50, 60, 70, 80, 90.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.5 tens = 50
- Add the ones. The ones are added on to the tens.50 + 4 = 54
- Write the number. 54
Check. Split 54 back into tens and ones: 5 tens and 4 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.7 tens = 70
- Add the ones. The ones are added on to the tens.70 + 4 = 74
- Write the number. 74
Check. Split 74 back into tens and ones: 7 tens and 4 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.2 tens
- Count the ones in each ten. Ten ones in every ten.2 x 10 = 20
- Write the answer. That is the total number of ones.20
Check. Count in tens to check: 10, 20.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Change the tens word to tens, then add the ones.
- Change the tens word. thirty is 3 tens.3 tens = 30
- Add the ones. Put the ones on the end.30 + 5 = 35
- Write the answer. 35
Check. 35 has 3 tens and 5 ones.
Watch out. Ask yourself: how many tens are in the number?
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.7 tens
- Count the ones in each ten. Ten ones in every ten.7 x 10 = 70
- Write the answer. That is the total number of ones.70
Check. Count in tens to check: 10, 20, 30, 40, 50, 60, 70.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.4 tens
- Look at the second digit. It is the number of ones.3 ones
- Write the answer. Say the tens, then the ones.4 tens and 3 ones
Check. 4 tens is 40, and 40 + 3 = 43.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.3 tens
- Count the ones in each ten. Ten ones in every ten.3 x 10 = 30
- Write the answer. That is the total number of ones.30
Check. Count in tens to check: 10, 20, 30.
Watch out. A ten is ten ones. Do not count the tens as ones.
Total 19 marks. Allow about 19 minutes.
Exercise 2X Practice test questions
Non-calculatorMethod. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.7 tens
- Count the ones in each ten. Ten ones in every ten.7 x 10 = 70
- Write the answer. That is the total number of ones.70
Check. Count in tens to check: 10, 20, 30, 40, 50, 60, 70.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.15
- Say its name. Each number from 0 to 20 has its own name.fifteen
- Write the answer. fifteen
Check. Count to 15 and stop on fifteen.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.4 tens
- Count the ones in each ten. Ten ones in every ten.4 x 10 = 40
- Write the answer. That is the total number of ones.40
Check. Count in tens to check: 10, 20, 30, 40.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.6 tens
- Count the ones in each ten. Ten ones in every ten.6 x 10 = 60
- Write the answer. That is the total number of ones.60
Check. Count in tens to check: 10, 20, 30, 40, 50, 60.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.thirteen
- Find the numeral. thirteen is the number 13.thirteen = 13
- Write the numeral. 13
Check. Count to 13 and check you say thirteen at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.
Method. Ten ones make one ten. So we count the tens and then multiply by ten.
- Count the tens. Each ten is a bundle of ten ones.5 tens
- Count the ones in each ten. Ten ones in every ten.5 x 10 = 50
- Write the answer. That is the total number of ones.50
Check. Count in tens to check: 10, 20, 30, 40, 50.
Watch out. A ten is ten ones. Do not count the tens as ones.
Method. Say the number name for each numeral from 0 to 20.
- Look at the numeral. It is less than 21.4
- Say its name. Each number from 0 to 20 has its own name.four
- Write the answer. four
Check. Count to 4 and stop on four.
Watch out. Some teen names look alike. Thirteen and thirty are different numbers.
Method. Put the tens together, then add the ones.
- Find the tens. Each ten is worth ten.3 tens = 30
- Add the ones. The ones are added on to the tens.30 + 0 = 30
- Write the number. 30
Check. Split 30 back into tens and ones: 3 tens and 0 ones.
Watch out. The ones are not added to the tens digit: 3 tens and 5 ones is 35, not 8.
Method. The tens digit tells us the tens. The ones digit tells us the ones.
- Look at the first digit. It is the number of tens.6 tens
- Look at the second digit. It is the number of ones.8 ones
- Write the answer. Say the tens, then the ones.6 tens and 8 ones
Check. 6 tens is 60, and 60 + 8 = 68.
Watch out. Read the digits from left to right. The left digit is the tens.
Method. Say the number name and find its numeral.
- Say the number name. Listen to the whole word.seven
- Find the numeral. seven is the number 7.seven = 7
- Write the numeral. 7
Check. Count to 7 and check you say seven at the end.
Watch out. Thirteen is 13: the 3 is at the end, as in the ones word.