Correct Answer - Option 1 : 70

**Given:**

Alcohol is 11.11% in 90 liters mixture.

**Calculation:**

Alcohol and water weighing 90 liters contains 11.11% alcohol.

Alcohol : water = 90 × (1/9) : 90 × (1/8)

⇒ Alcohol : water = 10 liters : 80 liters

Let the alcohol added in the mixture be x liters.

⇒ (10 + x)/80 = 1/1

⇒ x = 80 - 10

⇒ x = 70

**∴** **Alcohol should be added 70 liters****.**