Correct Answer - Option 1 : 6 Litres

**Given:**

Total solution of milk and water = 54L

Ratio of milk and water = 3 : 6

New ratio of milk and water = 2 : 3

**Calculation:**

Volume of milk = (3/9) × 54L = 18L

Volume of water = (6/9) × 54 = 36L

Let the new volume of milk added be x litre

⇒ (18 + x)/36 = 2/3

⇒ 54 + 3x = 72

⇒ 3x = 18

⇒ x = 6

**∴ 6 Litres of milk must be added to make the ratio of milk and water 2 : 3.**