White paint costs £2.80 per litre. Blue paint costs £3.50 per litre. White paint and blue paint are mixed in the ratio 3 : 2 Work out the cost of 18 litres of the mixture.

3:2 means there are 5 parts. So 18 litres can be divided by 5, and the price of each part worked out individuallly.

18 / 5 = 3.6

To work out how much the white paint costs: 3.6 x £2.80 = £10.08

£10.08 x 3 (as there are 3 white parts to 2 blue parts) = £30.24

To work out how much the blue paint costs: 3.6 x £3.50 = £12.60

£12.60 x 2 (as there are 2 blue parts to 3 white parts) = £25.20

Add these two amounts (£30.24 + £25.20) to get: £55.44