Ratio Notation

In a Nutshell

A ratio compares two or more quantities using a colon. The order matters.

A ratio tells you how much of one thing there is compared to another. We write ratios with a colon:

a:ba : b

This is read as "aa to bb". The order is important: 3:53 : 5 is not the same as 5:35 : 3.

For example, if a paint mix uses 2 parts blue to 3 parts white, we write the ratio of blue to white as 2:32 : 3.

The bar model below shows two quantities side by side. Change the values to explore different ratios.

Ratio bar model A bar split into 5 equal parts. 2 parts are shaded in the accent colour and 3 parts in a secondary colour, showing the ratio 2:3. 2 3 Ratio 2 : 3

Try changing the numbers. Notice how the bar adjusts to show the relative sizes.

Watch it work

Question: A bag has 4 red sweets and 6 green sweets. Write the ratio of red to green sweets.

Have a go

Q1. There are 5 cats and 8 dogs. Write the ratio of cats to dogs.

Q2. A recipe uses 200 g of flour and 50 g of sugar. Write the ratio of flour to sugar.

Q3. In a class, 12 students walk to school and 18 take the bus. Write the ratio of walkers to bus riders.

Q4. Write the ratio of vowels to consonants in the word "MATHS".