In 80 litres mixture of milk and water, the ratio of amount of milk to that of amount of water is 7 : 3. In order to make this ratio 2 : 1, how many litres of water should be added?

4 litres

Total Quantity of Mix of Milk and Water = 80 litres

Ratio of Milk M : Water W = 7: 3

M = 80 × (7x/10) = 56

W = 80 × (3x/10) = 24

Required Ratio = 2:1

Let us add "P" litres of water

56/(24+P) = 2/1

48+2P = 56

2P = 8

P = 4

The correct answer is Option (3) → 4 litres