A dishonest milkman professes to sell his milk at cost price but he mixes it with water and there by gains 25%. The percentage of water in the mixture is

This problem can be solved by understanding the concept of profit percentage and mixture.

1. The milkman gains 25% profit by selling the milk at the cost price. This means that the cost price of 1 litre of milk is the same as the selling price of 1.25 litres of the mixture (milk + water).

2. Since the selling price of the milk and the mixture is the same, the cost price of 1 litre of milk is equal to the cost price of 1.25 litres of the mixture.

3. Because water is free, the cost price of the mixture is entirely due to the milk in it. Therefore, 1 litre of milk is present in 1.25 litres of the mixture.

4. This means that 0.25 litres of water is present in 1.25 litres of the mixture.

5. Therefore, the percentage of water in the mixture is (0.25/1.25)*100 = 20%.

So, the milkman mixes 20% of water in the milk.