UPSC CAPF Assistant Commandant Model Paper 3

GIVEN:
Purchased milk from milkman = 16 L
Mixed quantity of water = 4 L
In process of making khoya, 50% of pure milk and 75% of water will vaporize.
After making khoya it weights 1 L less than original weight.
CALCULATION:
Original weight of khoya = 50% of 16 + 25% of 4 = 8 + 1 = 9 L
Let ‘x’ L water is mixed by milkman in the milk.
So,
Actual quantity of pure milk = (16 – x)
Quantity of water = (4 + x)
Actual quantity of khoya = 50% of (16 – x) + 25% of (4 + x) = 9 – 1
⇒ 8 – 0.5x + 1 + 0.25x = 8
⇒ 0.25x = 1
⇒ x = 4
∴ Required percentage = (4 / 16) × 100 = 25%