A ratio is a way of expressing the relationship between two amounts.

There are a number of different ways of writing down a ratio. For example, you could use ':' to separate two numbers, or write the ratio as a fraction or a percentage.

For example, the ratio of cows to giraffes in the picture could be expressed as

• \(5:4\) (for every 5 cows, there are 4 giraffes)
• \(\dfrac{5}{9}\) are cows and \(\dfrac{4}{9}\) are giraffes.
• \(0.55555555\dots\) are cows (dividing \(5\) by \(9\)).
• \(55.555\dots %\) are cows (\(0.55555555\dots\) as a percentage).