# Mixtures Alligation Practice Question

This aptitude practice question is a mixtures and alligation question. Concept tested: Ratio of mixture changes after adding more milk. A word problem in mixtures and alligation

## Question

A 20 litres mixture of milk and water comprising 60% pure milk is mixed with "x" litres of pure milk. The new mixture comprises 80% milk. What is the value of "x"?

1. 40 litres
2. 20 litres
3. 8 litres
4. 16 litres

Correct Answer      Choice (2). 20 litres

The quantity of the initial mixture of milk and water is 20 litres.
Out of the 20 litres, 60% is pure milk. i.e., 12 litres is milk and the remaining 8 litres is water.
When "x" litres of pure milk is added, we will have (12 + x) litres of milk in the new mixture.
And there will be 20 + x litres of the new mixture.

The question states that (12 + x) litres of milk accounts for 80% of (20 + x) litres of the mixture.
Therefore, 12 + x = $$frac{80}{100}$ *$20 + x)
12 + x = $$frac{4}{5}$ *$20 + x)
5(12 + x) = 4(20 +x)
60 + 5x = 80 + 4x
x = 20 litres

The correct answer is Choice (2).

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