Correct Answer - Option 3 : 5 litres
Given
Quantity of mixture = 40 litres
Water in mixture = 10%
Calculation
Quantity of Water in mixture = 10% 0f 40 = 4 litres
Quantity of Milk in mixture = 40 - 4 = 36 litres
There is 20% water in new mixture
∴ Ratio of water and milk is 20 : 80
⇒ 1 : 4
Let the quantity of water and milk in the new mixture be x and 4x
Water is added to make the new mixture, so the quantity of milk is constant throughout
⇒ 4x = 36
⇒ x = 9
So, Quantity of water in the new mixture is 9 litres
Quantity of water added = 9 - 4 = 5 litres