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.

Amount of paint needed:

White paint = (18 ÷ 5) × 3 = 10.8 litres

Blue paint = (18 ÷ 5) × 2 = 7.2 litres 

Cost of white paint = 10.8 x £2.80 = £30.24

Cost of blue paint = 7.2 x £3.50 = £25.20

Total cost = £30.24 + £25.20 = £55.44