Writing a comparison in the form of a ratio

Example

Five dogs and two cats of a variety of breeds

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.