How can multiples of ten make multiplication easier?

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Snoot and Fin use multiples of ten to help work out how much food their farm animals need.

Numbers like 2, 3 or 5 are quite small and straightforward.

Numbers like 20, 30 or 50 are bigger and the 0 at the end might seem confusing.

We call these numbers multiples of ten because we can think of them as numbers of groups of ten:

20 is 2 groups of 10

30 is 3 groups of 10

50 is 5 groups of 10

How can you multiply by multiples of 10?

If you have to multiply by 20, remember that this is 2 groups of 10, or 2 x 10.

So you might find it easier to multiply by 2 first, then multiply your answer by 10.

3 x 40 = ?

Remember that 40 is the same as 4 x 10

So first do 3 x 4 = 12

Then multiply this by 10

12 x 10 = 120

You've just worked out that 3 x 40 = 120

What about dividing? You can do something similar when dividing. First divide by the number of groups of 10, then divide by 10.

140 ÷ 20 = ?

Remember that 20 is the same as 2 x 10

So first do 140 ÷ 2 = 70

Then divide this by 10

70 ÷ 10 = 7

You've just worked out that 140 ÷ 20 = 7

Well done.