ratio

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Writing ratios

Ratios are similar to fractions; they can both be simplified by finding common factors. Always try to divide by the highest common factor.

To make pastry you may need to mix 2 parts flour to 1 part fat.

This means the ratio of flour to fat is 2:1.

It is sometimes useful to write a ratio in the form 1:n or n:1 (where n is any number, possibly a fraction or decimal). This means we will not necessarily be dealing with whole numbers.

If we are asked to write the ratio 2:5 in the form 1:n, we need to make the left-hand side of the ratio equal to 1. We do this by dividing both sides of the ratio by 2.

2:5 = 2/2 : 5/2

= 1 : 2.5

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Dividing in ratios

Ratios are also used when dividing up amounts.

Share £200 in the ratio 2:3

This means share the money into 5 equal parts and give one person 2 shares, and the other 3

So 200/5 = 40, one person gets 2 x £40 = £80 and the other 3 x £40 = £120

Check that this adds up to the total, in this case £200

Sometimes you are given one half of the ratio and you have to work out the total.

2100 is the '3' in 3:5

2100 divided by 3 = 700

700 x (3+5 = 8) = 5600