RatiosSimplifying ratios

Ratios are usually written in the form a:b and are used to compare quantities which are measured in the same units. Given a ratio, quantities can be calculated and are in direct proportion when they increase or decrease.

Part of MathsFractions, decimals and percentages

Simplifying ratios

can be fully simplified just like fractions.

To a ratio, divide all of the numbers in the ratio by the same number until they cannot be divided any more.

Example

Simplify \(6:12\).

Divide both numbers by 2:

\(6:12 = 3:6\)

Divide both numbers by 3:

\(3:6 = 1:2\)

A quick way of doing this in just one step is to divide by the of all the numbers in the ratio. In this example, the highest common factor of 6 and 12 is 6. Dividing each number by the HCF:

\(6:12 = 1:2\)

Image gallerySkip image gallerySlide 1 of 7, 6 red:12 yellow, A ratio of 6:12 with 6 red coloured counters and 12 yellow coloured counters spread out horizontally