A container contains some amount of milk. A milkman adds 200 ml of water for each one liter of milk in the container. 6 liters of the mixture is sold from the container and 10 litres of milk is added to the remaining mixture. If now the ratio of milk to water in container is 25: 3, find the initial quantity of milk in the container.

Let initial milk be M liters. Adding 200 ml water per liter gives M + 0.2M = 1.2M total mixture. Milk:water ratio is 5:1. When 6 liters is removed, milk removed = 6 × 5/6 = 5 liters, water removed = 6 × 1/6 = 1 liter. Remaining: M - 5 milk, 0.2M - 1 water. After adding 10 liters milk: total milk = M + 5, total water = 0.2M - 1. Given (M + 5)/(0.2M - 1) = 25/3. Cross-multiplying: 3M + 15 = 5M - 25, so 2M = 40, M = 20 liters.