In a mixture of 45 litres the ratio of milk to water is 4:1. Additional 11 litres of water is added to the mixture. Find the ratio of milk to water in the resulting mixture.  Pick one.
A) 2 / 1 B) 4 / 1 C) 2 / 3 D) 9 / 5 E) 3 / 2

Rationale: "given that milk / water = 4 x / x and 4 x + x = 45 - - > x = 9 . thus milk = 4 x = 36 liters and water = x = 9 liters . new ratio = 36 / ( 9 + 11 ) = 36 / 20 = 9 / 5 . answer : d ."
Answer: D