Mixtures Practice: Remove & Replace

This aptitude practice question is a mixtures and alligation question. Concept tested: Remove a part of a mixture and replace it with equal quantity of milk.

Question

How many litres of a 12 litre mixture containing milk and water in the ratio of 2 : 3 be replaced with pure milk so that the resultant mixture contains milk and water in equal proportion?

1. 4 litres
2. 2 litres
3. 1 litre
4. 1.5 litres

  Correct Answer      Choice (2). 2 litres

Explanatory Answer

The 12-litre mixture contains 40% milk and 60% water in it.
That is 4.8 litres of milk and 7.2 litres of water.

We are replacing the mixture with pure milk so that the amount of milk and water in the mixture is 50% and 50%.
So, we will end up with 6 litres of milk and 6 litres of water.
Water gets reduced by 1.2 litres.

To remove 1.2 litres of water from the original mixture containing 60% water, we need to remove \\frac{1.2}{0.6}) litres of the mixture = 2 litres.

  The correct answer is Choice (2).