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How can multiples of ten make multiplication easier?

Part of Maths and NumeracyNumbers and number processes

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

What are multiples of ten?

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.

Example

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.

Example

140 Ă· 20 = ?

Remember that 20 is the same as 2 x 10

So first do 140 Ă· 2 = 70

Then divide this by 10

70 Ă· 10 = 7

You've just worked out that 140 Ă· 20 = 7

Well done.

Snoot and Fin add and multiply to find out how many pests are in their kitchen.

How can adding help me multiply?

Fin and Snoot count meebs by putting them into equal rows and using multiplication.

How can an array help me multiply?

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