Answer:
£15.20
Explanation:
butter : sugar : flour = 2 : 1 : 9
Total mass for 1 recipe = 30 g
2 + 1 + 9 = 12
12x = 30
x = 30/12
x = 2.5
For 1 scone:
butter = 2x = 2(2.5) g = 5 g
sugar = x = 2.5 g
flour = 9x = 9(2.5) g = 22.5 g
Cost for 1 scone:
butter: 5 g × £2.50/(500 g) = £0.025
sugar: 2.5 g × £1.60/(1000 g) = £0.004
flour: 22.5 g × £0.6/(1500 g) = £0.009
Cost for 1 recipe = £0.025 + £0.004 + £0.009 = £0.038
Cost for 400 scones = 400 × £0.038 = £15.20
Answer: £15.20