Learn · number bonds
Number Bonds: What They Are and How to Teach Them
A number bond shows a whole and the two parts that make it. It's the picture behind most mental addition and subtraction.
A number bond is a pair of numbers that make a total, like 7 and 3 making 10. The total is the whole and the two numbers are the parts. Learn the bonds of 10 first, because so much else leans on them.
The picture
10 is the whole. 7 and 3 are the parts.
Why they matter
One bond gives four facts. From 10, 7 and 3 a child gets 7 + 3 = 10, 3 + 7 = 10, 10 − 7 = 3 and 10 − 3 = 7. That's the same set as a fact family, drawn as parts and a whole.
Bonds also make harder sums easy. 8 + 5 stops being a counting job once a child sees that 8 needs 2 to make 10, and 5 is 2 and 3. That's the make a ten strategy.
How to teach them
- Start with real objects. Put 5 blocks on the table, split them into two piles, and ask how many in each. Split them differently. The whole stays the same.
- Use ten-frames and fingers for the bonds of 10: look at the empty squares, or the folded fingers.
- Draw the bond with a missing part and ask what goes here? Our number bond sheets do this for any total.
- Play Bond Bridge: drag the plank that completes the bond. Quick recall comes from repeats like this.
Quick quiz: bonds to 10
Questions people ask
What's the difference between number bonds and fact families?
They're the same three numbers shown two ways. A number bond shows parts and a whole. A fact family writes out the addition and subtraction facts.
What are number bonds to 20?
Pairs that make 20, like 13 and 7. Each one comes from a bond to 10: 3 and 7 make 10, so 13 and 7 make 20. See bonds of 20.
What age should a child learn number bonds to 10?
Usually between 5 and 7. Bonds to 5 come first.
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