Question

From a flask containing water, 9 litres is taken out. It is replaced with an equal quantity of pure milk. This process is performed twice. The ratio of water to milk in the flask now is 16 : 9. What is the volume of the flask? (a) 45 litres (b) 65 litres (c) 50 litres (d) 75 litres

Answer 1

Let there be x litres in the cask.

After n operations,

Water left in vessel / Original quantity = (1 – 9/x)n

16/25 = (1 – 9/x)2

4/5 = 1 – 9/x

Answer 2

the answer is 1-9/x..