Correct Answer - Option 1 : 40 litres
Given
Ratio of milk and water = 4 ∶ 1
10 litres of water is added, then ratio is 3 ∶ 1
Calculation
Let the quantity of milk and water is 4x and x
According to question
4x/(x + 10) = 3/1
⇒ 4x = 3x + 30
⇒ 4x - 3x = 30
⇒ x = 30
∴ Quantity of water is 40 litres [(i.e. 30 + 10)]