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Age 7 guide to number bonds to 20

Age-appropriate activities, explanations and practice ideas for number bonds to 20.

Quick answer

By the end of this page, you'll know all the number bonds to 20 – that is, all the pairs of numbers that add up to 20.

Learning outcome

By the end of this page, you will be able to find all the number bonds to 20, and use them to solve simple addition problems. Success signs:
  • You can quickly say what number you need to add to any number from 1 to 19 to make 20
  • You can use number bonds to help solve addition problems
  • You can draw or use objects to show how two numbers make 20
  • You can play a game that uses number bonds to 20

Why this matters

Number bonds to 20 help you understand how numbers work together. They're useful for adding bigger numbers, solving word problems, and making mental maths easier. Knowing your number bonds helps you become more confident with maths in games, cooking, sports, and daily life.

How it works

Number bonds are pairs of numbers that add up to a certain total. For 20, you need to find all the ways to make 20 by adding two numbers together. Let’s start with small numbers and build up: 1. 0 + 20 = 20 2. 1 + 19 = 20 3. 2 + 18 = 20 4. 3 + 17 = 20 5. 4 + 16 = 20 6. 5 + 15 = 20 7. 6 + 14 = 20 8. 7 + 13 = 20 9. 8 + 12 = 20 10. 9 + 11 = 20 11. 10 + 10 = 20 This is a list of all the number bonds to 20. You can count them: there are 11 pairs.

Examples you can see

Let’s look at some fun ways to see number bonds to 20. Using objects: Imagine you have 20 toy cars. You can split them into two groups. For example:
  • 10 cars in one group, 10 cars in another group (10 + 10 = 20)
  • 7 cars in one group, 13 cars in another group (7 + 13 = 20)
  • 3 cars in one group, 17 cars in another group (3 + 17 = 20)
Using a number line: If you start at 0 and jump forward to 20, you can see how many steps it takes to get there. If you jump 12 steps, you land on 12. To get to 20, you need 8 more steps (12 + 8 = 20). Using a drawing: Draw 20 stars. Then, colour some stars red and some blue. If you have 9 red stars and 11 blue stars, you have 20 stars in total (9 + 11 = 20). Real-world example: You have 20 stickers to share with your friends. If you give 6 stickers to your friend, how many do you have left? That’s 20 – 6 = 14. So, 6 + 14 = 20.

Try it as a mini adventure

Adventure: The Treasure Hunt You are going on a treasure hunt. You start with 20 coins. You find a chest with 3 more coins. How many coins do you have now? (20 + 3 = 23). Wait, you need to go back to the start and only take 20 coins with you. So, you have 20 coins, and you found 3 more. That means you had 17 coins before finding the chest (17 + 3 = 20). Let’s play this game:
  1. Start with 20 coins
  2. Find 1 coin (20 + 1 = 21) – but you only take 20
  3. Find 2 coins (20 + 2 = 22) – but you only take 20
  4. Find 3 coins (20 + 3 = 23) – but you only take 20
  5. Find 4 coins (20 + 4 = 24) – but you only take 20
  6. Find 5 coins (20 + 5 = 25) – but you only take 20
  7. Find 6 coins (20 + 6 = 26) – but you only take 20
  8. Find 7 coins (20 + 7 = 27) – but you only take 20
  9. Find 8 coins (20 + 8 = 28) – but you only take 20
  10. Find 9 coins (20 + 9 = 29) – but you only take 20
  11. Find 10 coins (20 + 10 = 30) – but you only take 20
  12. Find 11 coins (20 + 11 = 31) – but you only take 20
  13. Find 12 coins (20 + 12 = 32) – but you only take 20
  14. Find 13 coins (20 + 13 = 33) – but you only take 20
  15. Find 14 coins (20 + 14 = 34) – but you only take 20
  16. Find 15 coins (20 + 15 = 35) – but you only take 20
  17. Find 16 coins (20 + 16 = 36) – but you only take 20
  18. Find 17 coins (20 + 17 = 37) – but you only take 20
  19. Find 18 coins (20 + 18 = 38) – but you only take 20
  20. Find 19 coins (20 + 19 = 39) – but you only take 20
Each time, you have 20 coins. If you find 1 coin, you had 19 before. If you find 2 coins, you had 18 before. If you find 3 coins, you had 17 before. This shows how the number bonds work!

Common mistakes

  • Mistake: Thinking that 10 + 10 = 21
    Why it happens: Confusing addition with counting
    Fix: Use objects or a number line to check: 10 + 10 = 20
  • Mistake: Forgetting that 0 + 20 = 20
    Why it happens: Not thinking about zero
    Fix: Remember that any number plus zero is itself
  • Mistake: Adding 10 + 10 and getting 100
    Why it happens: Confusing multiplication with addition
    Fix: Count carefully or use your fingers to check

Parent and carer guide

Parents and carers can help by:
  • Using everyday situations to practice number bonds (e.g., "You have 10 sweets, how many more do you need to make 20?")
  • Playing games like “What’s the missing number?”
  • Using counters, blocks, or toys to show the bonds
  • Encouraging children to say the bonds out loud to build memory
  • Not pushing too hard – make it fun and relaxed
What to say:
  • "Can you show me how 7 and 13 make 20?"