Correct Answer - Option 3 :

\(2\frac{2}{9}\)
**Calculation:**

5% of 40 liters

⇒ 5/100 × 40

⇒ 2 liters

In total mixture,

Out of 40 liters, water is 2 liters.

⇒ Milk = 40 – 2 = 38 liters

Now when water is 10% then milk will be 90%

According to the question,

⇒ 90% = 38 liters

⇒ 10% = 38/9 liters

Increased quantity of water,

⇒ 38/9 – 2 = (38 – 18)/9

⇒ 20/9

⇒ \(2\frac{2}{9}\)

**∴ The amount of water that needs to be added is \(2\frac{2}{9}\)liters.**