CDS 2015 PYQ with Answer — In a mixture of milk and water of volume 30 litre, the ratio of milk…

2015 · Q89

In a mixture of milk and water of volume 30 litre, the ratio of milk and water is 7:3. The quantity of water to be added to the mixture to make the ratio of milk and water 1:2 is

Elementary MathematicsTrigonometry

Explanation

This is a mixture problem where one component stays fixed. The 30 L mixture at 7:3 contains 21 L milk and 9 L water; only water is added, so milk stays at 21 L. For the new ratio 1:2, water must become 2 × 21 = 42 L, so 42 - 9 = 33 L of water must be added. The trap is option (a) 30 L, from naively adding water equal to the mixture's volume. Hence option (c).