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.

Understanding of the ratio: 2+3=5, 3/5 is white, 2/5 blue, 2.818(3/5) + 3.518(2/5) No calculator paper, so check ability to do accurately arithmetic as above and make sure to think about the answer as common sense, the correct order of magnitude.