NUMBER BEASTS

Number bonds to 10, 20, 50 and 100

Number bonds are pairs of numbers that add up to a total. This guide lists every pair for 10, 20, 50 and 100, with quick tips for learning them.

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Frequently asked questions

What are number bonds?

Number bonds are pairs of numbers that add up to a given total. For example, 6 and 4 are a number bond to 10 because 6 + 4 = 10. Knowing them by heart makes mental addition and subtraction much faster.

How many number bonds to 10 are there?

Using whole numbers from 1 to 9 there are five different pairs: 1 + 9, 2 + 8, 3 + 7, 4 + 6 and 5 + 5 (nine ordered pairs if you count 9 + 1 separately; eleven if you include 0 + 10 and 10 + 0).

What is the fastest way to learn bonds to 100?

Start with multiples of ten (30 + 70), then multiples of five (35 + 65), then any pair. A useful trick: the tens add to 90 and the ones add to 10, so 37 + 63 works because 30 + 60 = 90 and 7 + 3 = 10.

How does Number Beasts help?

Every correct pair you connect launches energy balls into the arena, so practice becomes an arcade game. It is free on the web and on iPhone and iPad.

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