A container contains a mixture of milk and water in the ratio of 3 : 7. If 20 litres of the mixture is replaced with water, the ratio of milk to water becomes 1 : 4. What was the initial quantity of the mixture in the container?

Let the initial quantity of the mixture be x liters, meaning the container has 0.3x liters of milk. Removing 20 liters removes 6 liters of milk, leaving 0.3x minus 6 liters of milk. Since the final ratio of milk to water is 1 to 4, milk constitutes 20% of the new total, so 0.3x minus 6 equals 0.2 multiplied by x. Solving this gives 0.1x equals 6, so the initial quantity is 60 liters.

• Thanks
• Wrong explanation