A can holds 120 litres of milk and water in the ratio 5 : 1. How many litres of the mixture must be drawn off and replaced with water so that the ratio becomes 3 : 1?
Correct answer C. 12 litres
Explanation
Milk fraction must fall from 5/6 to 3/4. (1 - x/120) x 5/6 = 3/4 gives 1 - x/120 = 9/10, so x = 12 litres.
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