How can near doubles help me add numbers?

Snoot and Fin use near doubles to help them add two similar numbers.

Are you good at doubling numbers? This can help you add numbers that are close to each other.

The trick is to double a number that you know and then add on or take away the difference.

If you know that 10 + 10 = 20 then this can help you work out 10 + 11.

10 + 11 is the same as 10 + 10 + 1 which makes 21.

Example

9 + 12 = ?

9 and 12 are both close to 10.

10 + 10 = 20

9 is 1 less than 10, so take this away.

20 – 1 = 19

That leaves the 12. It is 2 more than 10 so you need to add this on.

19 + 2 = 21

You’ve just worked out that 9 + 12 = 21.

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