Correct Answer  Option 2 : 3 litres
Given:
Ratio

Alcohol ∶ Water

Old

11 ∶ 6

New

5 ∶ 3

Calculation:
Let the water that should be added be x litres
Initial quantity of alcohol = [11/(11 + 6)] × 85 litres
⇒ (11/17) × 85 litres
⇒ 55 litres
And, initial quantity of water = [6/(11 + 6)] × 85 litres
⇒ (6/17) × 85 litres
⇒ 30 litres
Now, [55/(30 + x)] = (5/3)
⇒ 11 × 3 = (30 + x)
⇒ x = 33 – 30
⇒ x = 3 litres
∴ 3 litres water should be added to make the ratio 5 ∶ 3.