Percentage of a quantity

Question

Concrete is sometimes made from 1 part cement, 4 parts blue metal and 3 parts sand. Find the percentage of cement used

Answer 1

The percentage of cement used is $(\frac{1}{1+4+3}\times 100)\%$.

Answer 2

There is a total of 8 parts in any quantity of concrete: 1 part cement, 4 parts metal and 3 parts sand. 1 part out of 8 parts total is cement. This gives us 1/8 = 0.125 = 12.5% cement.