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A ratio shows how much of one thing there is compared to another.

Ratios are usually written in the form:

a:b

If you are making orange squash and you mix one part orange to four parts water, then the ratio of orange to water will be 1:4 (1 to 4).

The order in which a ratio is stated is important. Changing the order of the numbers in a ratio changes the proportions.

The ratio of red to blue dinosaurs is 12:18.

This ratio can be simplified. Both 12 and 18 can be divided by 2.

12 ÷ 2 = 6

18 ÷ 2 = 9

So a simpler way to write 12:18 is 6:9.

12:18 = 6:9

The ratio can be made simpler again, if we divide by 3.

6 ÷ 3 = 2

9 ÷ 3 = 3

So an even simpler way to write 12:18 is 2:3.

12:18 = 2:3