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What Are Number Bonds? Explained For Primary Parents And Kids

Number bonds are pairs of numbers that can be added together to make another number e.g. 4 + 6 = 10. They are some of the most basic and most important parts of maths for children to learn.

What are number bonds?

A number bond is a pair of numbers that always add together to make another, larger, number. Children are introduced to this concept through number bonds to 10:

  • 0 + 10
  • 1 + 9
  • 2 + 8
  • 3 + 7
  • 4 + 6
  • 5 + 5

These are the foundations of many other key number bonds – if children can fluently recall their number bonds to 10, they will be able to calculate number bonds to other multiples of 10.

number bonds to 10
Number bonds to 10 illustration

This can then be developed to larger multiples of 10 (such as multiples of 100) and even decimal number bonds (e.g. 0.3 + 0.7 = 1). Children should also be able to calculate the corresponding subtraction facts for these number bonds, e.g. if 1 + 9 = 10, then 10 – 1 = 9 and 10 – 9 = 1.

Read more: Teaching Addition & Subtraction at KS2

FREE Partitioning Numbers Worksheet

FREE Partitioning Numbers Worksheet

This time-saving worksheet is for Year 1 partitioning numbers and includes 4 arithmetic questions, 9 consolidation questions, and 1 challenge question.

Number bonds to 10

The number bonds to 10 are

  • 0 + 10
  • 1 + 9
  • 2 + 8
  • 3 + 7
  • 4 + 6
  • 5 + 5
  • 6 + 4
  • 7 + 3
  • 8 + 2
  • 9 + 1
  • 10 + 0

Number bonds to 20

The number bonds to 20 are

  • 0 + 20
  • 1 + 19
  • 2 + 18
  • 3 + 17
  • 4 + 16
  • 5 + 15
  • 6 + 14
  • 7 + 13
  • 8 + 12
  • 9 + 11
  • 10 + 10
  • 10 + 10
  • 11 + 9
  • 12 + 8
  • 13 + 7
  • 14 + 6
  • 15 + 5
  • 16 + 4
  • 17 + 3
  • 18 + 2
  • 19 + 1
  • 20 + 0

Number bonds to 100

Number bonds to 100 are pairs of numbers that add together to make 100 such as 20 + 80, or 55 + 45. To find the number bond pair for any number use your knowledge of number bonds to 10 to work out first what the matching unit or ‘ones’ would be to bridge to the next ten and then, what the number pair would be for the tens.

So for example to find the number bond to 100 of 36, you first add 4 to reach 40, then add 60 to reach 100. So the number bond to 100 of 36 is 64.

When will my child learn about number bonds in primary school?

Your child may already have come across number bonds in EYFS, but the National Curriculum introduces the concept at Key Stage 1 in Year 1, where children will represent and use number bonds and related subtraction facts within 20.

The non-statutory guidance also advises that Year 1 pupils memorise and reason with number bonds to 10 and 20 in several forms (for example, 9 + 7 = 16; 16 – 7 = 9; 7 = 16 – 9). The NC states that by the end of year 2, pupils should know the number bonds to 20 and be precise in using and understanding place value. An emphasis on practice at this early stage will aid fluency.

Third space learning online maths intervention year 1 number bonds slide
Introducing number bonds to Year 1 pupils in Third Space Learning’s online maths intervention.

Wondering about how to explain other key maths vocabulary to your children? Check out our Primary Maths Dictionary, or try these other terms related to number bonds:

Number bonds practice questions

1. Complete these addition sums. One is done for you.

3 + 7 = 10
33 + __ = 40
__ + 7 = 80

(Answer: 7 and 73)

2. Write missing numbers on the lines to make this correct.

60 + __ = 100 = 20 + ___

(Answer: 40 and 80)

3. Write the next three sums in the pattern:

1 + 9 = 10
2 + 8 = 10
3 + 7 = 10

(Answer: 4+6, 5+5, 6+4)

4. Use your knowledge of number bonds to answer this calculation:

7 + 2 + 1 + 8 + 9 + 3

(Answer: 30)

Number bonds games

Number bonds are often taught in school through maths games and maths problems. As well as these number bonds to 10 activities we also have several games specifically for practising number facts and number bonds including these fun maths games for kids at home or school, KS1 maths games, Key Stage 2 maths games and then these mental maths games.

You can also use manipulatives to develop practice number bonds in a hands-on way, such as a tens frame.

Number bonds worksheets

Take a look at the Third Space Learning Maths Hub to get access to hundreds of free resources and premium maths worksheets, including some of the following for number bonds:

What is an example of number bonds?

Number bonds are pairs of numbers that can be added together to make another number e.g. 4 + 6 = 10.

What age do you teach number bonds?

Child may come across number bonds in EYFS, but the primary curriculum introduces the concept in Year 1. By the end of Year 2, pupils should know the number bonds to 20.

Why should children know number bonds?

Learning number bonds and using them with fluency will help children as they learn addition, subtraction and times tables.

Do you have students who need extra support in maths?
Every week Third Space Learning’s maths specialist tutors support thousands of students across hundreds of schools with weekly online 1-to-1 lessons and maths interventions designed to address learning gaps and boost progress.

Since 2013 we’ve helped over 150,000 primary and secondary students become more confident, able mathematicians. Learn more or request a personalised quote for your school to speak to us about your school’s needs and how we can help.

Primary school tuition targeted to the needs of each child and closely following the National Curriculum.

Sophie Bartlett
Sophie Bartlett
Year 6 Teacher
Sophie teaches mixed age classes at a small school in central England. She is a self confessed grammar pedant and number nerd so we've welcomed her as a regular author and editor for Third Space Learning.
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FREE Partitioning Numbers Worksheet

FREE Partitioning Numbers Worksheet

This time-saving worksheet is for Year 1 partitioning numbers and includes 4 arithmetic questions, 9 consolidation questions, and 1 challenge question.

Download Free Now!

FREE Partitioning Numbers Worksheet

Downloadable resource

This time-saving worksheet is for Year 1 partitioning numbers and includes 4 arithmetic questions, 9 consolidation questions, and 1 challenge question.

Download Free Now!
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FREE Long Division Worksheets for KS2

3 ready to use worksheets for your class that will help them with all aspects of long division from 1-digit numbers through to working out multiples!

One worksheet covering division with 1-digit numbers, one covering 2-digit numbers and one for working out multiples.

Download free