What is a Ratio?

A ratio is a comparison in terms of a quotient of two numbers a and b, usually written as $ \frac{a}{b} $ or a/b.

Science regularly requires us to compare values. Ratios are used to compare the amount of one number to another number.

Ratios can be expressed as;

                    1 to 5                     1 : 5                        $ \frac15 $ or 1 / 5

No matter which notation is used for this ratio, it is read as "1 to 5".

You will have probably encountered ratios in your everyday life. Some potential examples include;

  • The ratio of girls to boys in a class is 4 : 3
  • A pancake recipe requires a flour to milk ratio of 3 : 2
  • A model aeroplane has a scale of 1 : 48

 Ratios should be expressed in their simplest form. For example, a ratio of 25 to 5 can be simplified to;

$ \frac{25}{5} = \frac51 $ or 25/5 = 5/1. For example, a laboratory solution contains 58.5 grams of NaCl per litre. Expressed as a ratio, this would be 58.5g / 1 L

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