A ratio is used to compare two quantities which are measured in the same units. Given a ratio, quantities can be calculated.

A farmer has 2 cats and 5 dogs. Write down the ratio of cats to dogs and dogs to cats.

Cats : Dogs \(= 2 : 5\)

Dogs : Cats \(= 5 : 2\)

Now try this question:

- Question
The same farmer also has 85 sheep and 15 cows. Write down the ratio of cows to sheep in its simplest form.

cows : sheep \(= 15 : 85\)

\(15\) and \(85\) are both divisible by 5

\[\frac{{15}}{5} = 3\]

\[\frac{{85}}{5} = 17\]

So \(15 : 85 = 3 : 17\)

A ratio is used to compare two quantities which are measured in the same units.