Number bonds
Pairs of numbers that make 10, 20 or 100: the facts behind quick adding and taking away. See them on a ten frame, then play to make them stick.
Owl Post
Thena’s owl has letters to deliver. Each door has a sum on it: pick the letter with the answer and light up the village.
What is a number bond?
Two numbers that make a whole: 7 and 3 make 10. Schools draw it as a part-whole model, the whole in one circle and its parts in two below, and build it with two-coloured counters on a ten frame. Turn the counters over and watch the bond change.
Tap a counter to turn it over.
7 and 3 make 10.
- 7 + 3 = 10
- 3 + 7 = 10
- 10 − 7 = 3
- 10 − 3 = 7
One bond gives two additions and two subtractions.
Every number bond to 10, 20 and 100
Bonds to 10
- 0 + 10 = 10
- 1 + 9 = 10
- 2 + 8 = 10
- 3 + 7 = 10
- 4 + 6 = 10
- 5 + 5 = 10
- 6 + 4 = 10
- 7 + 3 = 10
- 8 + 2 = 10
- 9 + 1 = 10
- 10 + 0 = 10
Bonds to 20
- 0 + 20 = 20
- 1 + 19 = 20
- 2 + 18 = 20
- 3 + 17 = 20
- 4 + 16 = 20
- 5 + 15 = 20
- 6 + 14 = 20
- 7 + 13 = 20
- 8 + 12 = 20
- 9 + 11 = 20
- 10 + 10 = 20
- 11 + 9 = 20
- 12 + 8 = 20
- 13 + 7 = 20
- 14 + 6 = 20
- 15 + 5 = 20
- 16 + 4 = 20
- 17 + 3 = 20
- 18 + 2 = 20
- 19 + 1 = 20
- 20 + 0 = 20
Bonds to 100, in tens
- 0 + 100 = 100
- 10 + 90 = 100
- 20 + 80 = 100
- 30 + 70 = 100
- 40 + 60 = 100
- 50 + 50 = 100
- 60 + 40 = 100
- 70 + 30 = 100
- 80 + 20 = 100
- 90 + 10 = 100
- 100 + 0 = 100
Once bonds to 10 come quickly, the rest follow: 3 and 7 make 10, so 13 and 7 make 20, and 30 and 70 make 100.
How schools teach them
In England, bonds start in Reception and build to 100 by Year 2 and Year 3, following the National Curriculum.
- Reception
- Recalling number bonds up to 5, and some to 10, including doubles, without counting.
- Year 1
- Number bonds and their subtraction facts within 20, shown with objects and pictures.
- Year 2
- Addition and subtraction facts to 20 recalled fluently, and used for related facts to 100, like 30 + 70 = 100.
- Year 3
- Bonds used for mental adding and taking away, including two-digit pairs that make 100, like 37 and 63.
Number bonds at home
On their fingers
Hold up 6 fingers: how many are down? Ten fingers are a bond to 10 that’s always with them.
Make 10 snap
Take the cards from ace to 9 out of a pack. Turn two over at a time: if they make 10, the first to say so keeps them.
Say the family
For every bond, say all four facts: 4 + 6, 6 + 4, 10 − 4 and 10 − 6. Taking away comes free.
Scale it up
When 3 and 7 are quick, ask 30 and what? Then 13 and what makes 20? One fact, three bonds.
More to try
Questions about number bonds
What are number bonds to 10?
The pairs of whole numbers that add up to 10: 0 and 10, 1 and 9, 2 and 8, 3 and 7, 4 and 6, and 5 and 5, plus the same pairs swapped, like 7 and 3.
How many number bonds to 10 are there?
Eleven, counting each order: 0 + 10, 1 + 9 and so on up to 10 + 0. That’s six different pairs if 3 + 7 and 7 + 3 count as one.
What’s the difference between number bonds and fact families?
A number bond is a pair and its whole: 3 and 7 make 10. Its fact family is the four facts that bond gives you: 3 + 7 = 10, 7 + 3 = 10, 10 − 3 = 7 and 10 − 7 = 3.
Why do number bonds matter?
They make adding and taking away quick. 8 + 5 is 8 + 2 + 3, which is 13, because 8 and 2 make 10. Bonds to 100 help with money, time and measuring later on.
When it doesn’t click
Thena draws bonds on her ten frame as she explains them, and keeps going until your child sees it for themselves.
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