60 litres of a mixture have milk and water in the ratio 3 : 1. How much water must be added to make the ratio 3 : 2?

Explanation

1. 01

   Milk $= \frac{3}{4} \times 60 = 45$ litres and water 15 litres.

2. 02

   For 3 : 2, water must be $\frac{2}{3} \times 45 = 30$ litres: add $30 - 15 = 15$ litres.