Ratio - GCSE Maths Definition

A ratio is a way to express the proportion of two or more quantities relative to each other, compared to the whole. This is done by splitting the whole into 'parts'. For example, in the ratio 3:2, the first quantity is worth three parts of the whole, the second quantity is worth two parts of the whole; clearly, the whole is made up of five parts.

Ratio, proportion and fractions are closely linked. In the first instance, ratio compares the proportion of each quantity to the other quantities (rather than to the whole, like a fraction would).