In a mixture of 45 litres the ratio of milk to water is 4:1. Additional 12 litres of water is added to the mixture. Find the ratio of milk to water in the resulting mixture.  Pick one:
A) 12 / 7 B) 4 / 1 C) 2 / 3 D) 3 / 4 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 + 12 ) = 36 / 21 = 12 / 7 . answer : a ."
Answer: A