X Tables
Educational Maths Games

Topmarks Hit the Button maths: number bonds

Use age-appropriate, adult-approved play examples to practise quick recall of pairs that make 10, 20 or 100.

Quick answer

Number bonds are pairs of numbers that add up to a specific total, like 3 and 7 making 10. Topmarks Hit the Button is a fun online game where you quickly find these number bonds to improve your mental maths speed and accuracy.

Learning outcome

By the end of this page, you will know how to quickly find pairs of numbers that make 10, 20, or 100 – and you'll be able to play Topmarks Hit the Button maths games with confidence! Success signs:
  • You can instantly say what number pairs with 6 to make 10
  • You can quickly spot number bonds for 20 and 100
  • You can play Topmarks Hit the Button and get fast scores
  • You understand that number bonds help you solve bigger maths problems

Why this matters

Number bonds are the foundation of addition and subtraction. When you know your number bonds, you can solve problems faster and more confidently. Whether you're sharing 10 biscuits with a friend, counting your pocket money, or playing a maths game like Topmarks Hit the Button, knowing number bonds helps you think quickly and accurately. In school, number bonds help you:
  • Learn your times tables more easily
  • Understand how numbers fit together
  • Do mental maths faster
  • Build strong number sense
Whether you're playing a game, cooking, or saving up for a toy, number bonds are useful everywhere!

How it works

Number bonds are pairs of numbers that add up to a given total. For example:
  • 3 + 7 = 10, so 3 and 7 are number bonds for 10
  • 12 + 8 = 20, so 12 and 8 are number bonds for 20
  • 45 + 55 = 100, so 45 and 55 are number bonds for 100
You can find number bonds by:
  1. Starting with one number
  2. Thinking, "What number do I need to add to get to the total?"
  3. Checking your answer by adding them together
Let’s start with smaller numbers and build up.

Examples you can see

Let’s explore number bonds for 10:
Number Bond to 10 Check
1 9 1 + 9 = 10
2 8 2 + 8 = 10
3 7 3 + 7 = 10
4 6 4 + 6 = 10
5 5 5 + 5 = 10
These pairs are all number bonds for 10. Notice how 5 + 5 = 10 – that’s a special pair because both numbers are the same! Now let’s look at number bonds for 20:
Number Bond to 20 Check
1 19 1 + 19 = 20
2 18 2 + 18 = 20
3 17 3 + 17 = 20
4 16 4 + 16 = 20
5 15 5 + 15 = 20
And for 100:
Number Bond to 100 Check
10 90 10 + 90 = 100
20 80 20 + 80 = 100
30 70 30 + 70 = 100
40 60 40 + 60 = 100
50 50 50 + 50 = 100
You can also use your fingers or draw dots to help you find these pairs.

Try it as a mini adventure

Adventure: The Number Bond Quest You are on a treasure hunt! To open the treasure chest, you must find the number bond that makes 10, 20, or 100. You have a magic number, and you must find its partner to unlock the next clue. 1st time: You see the number 7. What number bonds with 7 to make 10? Answer: 3 2nd time: You see the number 12. What number bonds with 12 to make 20? Answer: 8 3rd time: You see the number 35. What number bonds with 35 to make 100? Answer: 65 4th time: You see the number 9. What number bonds with 9 to make 10? Answer: 1 5th time: You see the number 15. What number bonds with 15 to make 20? Answer: 5 Keep going – can you find all the number bonds in 10 seconds?

Common mistakes

  • Mistake: Thinking 7 + 4 = 10, but 7 + 4 = 11.
    Why it happens: Quick thinking can make you add numbers wrong.
    Fix: Count on your fingers or use a number line to double-check.
  • Mistake: Forgetting that 5 + 5 = 10.
    Why it happens: When numbers are the same, it’s easy to forget the answer.
    Fix: Practice saying 5 + 5 = 10 out loud a few times.
  • Mistake: Not knowing that 100 = 50 + 50.
    Why it happens: Big numbers can be confusing.
    Fix: Break it into smaller parts – 50 + 50 = 100.
  • Mistake: Confusing 20 with 100.
    Why it happens: Big numbers can be tricky to tell apart.
    Fix: Use visual tools like counters or drawings to help you see the difference.

Parent and carer guide

Parents and carers, here’s how to help your child learn number bonds in just 5–10 minutes:
  • Play Topmarks Hit the Button together – it’s a fun way to practice
  • Use everyday moments: “If you have 3 sweets and I give you 7 more, how many do you have?”
  • Draw number bond circles: draw a circle and split it into two parts – one part is 6, the other part is 4. Together they make 10!
  • Use physical objects like blocks or coins to show number bonds
  • Encourage your child to say number bonds out loud – it helps with memory
  • Don’t worry if they make mistakes – it’s part of learning!
You can also try:
  • Counting in 10s to 100 to build up to bigger number bonds
  • Using a number line to help find missing numbers
  • Playing games like “What’s the number bond?” with flashcards

Practice questions

  1. What number bonds with 4 to make 10? Answer: 6
  2. What number bonds with 13 to make 20? Answer: 7
  3. What number bonds with 25 to make 100? Answer: 75
  4. What number bonds with 9 to make 10? Answer: 1
  5. What number bonds with 18 to make 20? Answer: 2
  6. What number bonds with 30 to make 100? Answer: 70
  7. What number bonds with 6 to make 10? Answer: 4
  8. What number bonds with 11 to make 20? Answer: 9
  9. What number bonds with 40 to make 100? Answer: 60
  10. What number bonds with 2 to make 10? Answer: 8

FAQ

What are number bonds?

Number bonds are pairs of numbers that add up to a given total. For example, 3 and 7 are number bonds for 10.

Why do we learn number bonds?

Number bonds help you solve addition and subtraction problems faster. They also make it easier to learn your times tables later.

How can I practice number bonds at home?

You can use flashcards, play Topmarks Hit the Button, or count objects like coins or blocks to find number bonds.

What’s the best way to learn number bonds?

Practice them daily with games, drawings, and real-life examples. The more you use them, the faster you’ll get.

Are number bonds only for small numbers?

No! You can find number bonds for 10, 20, 100, and even bigger numbers. As you get better, you’ll learn to work with larger totals.