Correct Answer - Option 2 : 84.1 litres

**Given:**

The initial quantity of alcohol in the container = 90 litres

Quantity of water added each time = 3 litres

**Formula used:**

Alcohol left in container = [1 – (N/Q)]^{T} × Q

Where N = Quantity Removed

Q = Initial total quantity

T = Times of repetition

**Calculation:**

The final quantity of Alcohol in the container = [1 – (N/Q)]^{T} × Q

⇒ [1 – (3/90)]^{2} × 90 litres

⇒ [(90 – 3)/90]^{2} × 90 litres

⇒ (87/90)^{2} × 90 litres

⇒ 84.1 litres

**∴ 84.1 litres of alcohol**** left in the final mixture.**