What are number bonds?
A plain-English guide for parents · Primary 1
A number bond shows how a whole number splits into two parts — and how those
parts join back into the whole. That's the entire idea.
10 splits into 7 and 3
7 + 3 = 10 · 3 + 7 = 10 · 10 − 7 = 3 · 10 − 3 = 7
In your child's workbook it's usually drawn as a circle for the whole with two circles branching
off it for the parts. Same idea, just a picture.
Why schools make such a fuss about them
Because a child who truly knows their bonds stops counting on fingers. Instead of working out
8 + 5 one finger at a time, they think: 8 needs 2 to make 10, and 5 is 2 and 3, so it's 10 and 3
— 13. That "making 10" move is the foundation of mental arithmetic, and it comes straight out of
number bonds.
It also quietly teaches that addition and subtraction are the same relationship seen from different
directions. A child who sees that 10 − 7 = 3 is just the 7-and-3 bond read backwards
finds subtraction far less frightening.
The bonds worth knowing by heart
Bonds to 10 are the ones that matter most in P1. There are only six to learn, because the reverse
of each is free:
| Bond | Also means |
|---|
| 1 and 9 | 9 and 1 |
| 2 and 8 | 8 and 2 |
| 3 and 7 | 7 and 3 |
| 4 and 6 | 6 and 4 |
| 5 and 5 | — |
| 0 and 10 | 10 and 0 |
Once bonds to 10 are automatic, the same thinking extends to 20, then to 100.
How to help at home, in five minutes
- Say a number, they say the partner. You say "6", they say "4". Do it while
queueing, in the car, brushing teeth. Thirty seconds at a time beats a worksheet.
- Use real objects first. Ten buttons, split into two piles. Let them physically
see that moving one button changes both parts.
- Hide some. Show ten sweets, cover four with your hand, ask how many are hidden.
This is subtraction, but it feels like a game.
- Ask "how do you know?" The explanation matters more than the answer. A child
who can explain it, owns it.
Watch for this: a child who answers correctly but slowly, by counting up in their
head, hasn't learnt the bond yet — they've just found a workaround. Fluency is the goal, and it
only comes from short, frequent practice.
Common mistakes
- Mixing up whole and part. Given the whole is 10 and one part is 6, some
children answer 16 — they add instead of finding the missing part. Going back to physical objects
usually fixes this quickly.
- Learning only one direction. They know 7 + 3 but freeze at 10 − 3. Practise
both ways from the start.
- Rushing to bigger numbers. Bonds to 20 are much easier once bonds to 10 are
genuinely automatic. There's no prize for skipping ahead.
Practise it free
StudyLab has a Number Bonds game for Primary 1 — it asks things like "7 and ❓ make 10", with no
ads, no sign-up and nothing to install. Progress saves on your own device.
Practise number bonds →