Correct Answer - Option 3 : 100
Calculation:
Amount of Alcohol in the solution = 100 × (20/100) = 20 Litres
Let P be the added water,
⇒ (100 + P) × (10/100) = 20
⇒ 100 + P = 200
⇒ P = 100 Litres
If a mixture of Q1 quantity C1% content is mixing with Q2 quantity C2% mixture, and the concentration of the new mixture is Cnew% , then the following equation can be used
C1% of Q1 + C2% of Q2 = Cnew% of (Q1 + Q2)
⇒ C1Q1 + C2Q2 = Cnew(Q1 + Q2)