A container is filled with 60 litres of pure milk. 12 litres are drawn out and replaced with water, and then this is repeated once. What is the ratio of milk to water now?

Explanation

1. 01

   Each operation keeps $\frac{48}{60} = \frac{4}{5}$ of the milk.

2. 02

   Milk = $60 \times \left(\frac{4}{5}\right)^2 = 38.4$ litres; water = $60 - 38.4 = 21.6$ litres.

3. 03

   Milk : water = $38.4 : 21.6 = 384 : 216 = 16 : 9$.