Question

200 litres of a mixture contains 15% water and the rest is milk. the amount of milk that must be added so that the resulting mixture contains 87.5% milk is

Answer 1

The initial amount of milk is :

85/100 × 200 = 170 litres

Let the amount of milk to be added be x then :

The new amount of milk is :

x + 170 litres

The total amount of mixture becomes :

200 + x

We express the new quantity of milk as a percentage of the total mixture as follows.

(x + 170) / (x + 200) × 100 = 87.5

100x + 17000 = 87.5x + 17500

100x - 87.5x = 17500 - 17000

12.5x = 500

x = 40

We therefore add 40 litres of milk.