A dishonest milkman professes to sell his milk at cost price but he mixes it with water and thereby gains 25%. What is the percentage of water in the mixture? MCQ with Answer and Explanation

Let the CP of 1 liter of pure milk be Rs. 1. SP of 1 liter of mixture is Rs. 1. Gain is 25%. Thus, CP of 1 liter of mixture = 100/125 * 1 = Rs. 0.8. Using alligation, ratio of milk to water is (1 - 0.8) : (0.8 - 0) = 0.8 : 0.2 = 4:1. Percentage of water in the mixture = (1 / (4 + 1)) * 100 = 20%.