200 litres of a mixture contains milk and water in the ratio 17 : 3. After the addition of some more milk to it, the ratio of milk to water in the resulting mixture becomes 7 : 1. The quantity of milk added to it was =?

Answer: Option B

Milk : water = 17 : 3 = 17x : 3x
∴ 17x + 3x = 200
⇒ x =10 litre
Milk = 170 litre and water = 30 litre in initial mixture.
Let 'y' litre of milk added in mixture
i.e. 170 + y : 30 = 7 : 1
⇒ $$\frac{170+y}{30}=\frac{7}{1}$$
∴ y = 210 - 170 = 40 litre