To distribute a quantity according to a ratio, carry out the following steps:

• Work out the total number of parts in the ratio;

• Divide the quantity by the number of parts;

• Multiply quantity in each part by the ratio amount.

There are 48 cars in a car park. If the ratio of red cars to other cars is 3:5, how many red cars were there?

There are 3 + 5 = 8 parts altogether.

Number of cars in each part = 48 ÷ 8 = 6

Number of red cars = number of red parts x cars in each part

red cars = 3 x 6 = 18

Answer: 18

Cement is being mixed with sand to make concrete in the ratio 1:5. If a total of 150kg of concrete is required, how much cement and sand is needed?

The ratio is 1:5. Add the parts 1 + 5 = 6 parts altogether.

Divide 150kg by 6 = 25kg per part.

Cement is 1 part x 25 = 25

Sand is 5 parts x 25 = 125.

Check by adding together: 25 + 125 = 150✔

Answer: Cement: 25kg; Sand 125kg

Check out our iOS app: tons of questions to help you practice for your GCSE maths. Download free on the App Store (in-app purchases required).