Correct Answer - Option 4 : 10

**Given:**

Mixture of acid and alcohol in the ratio = 3 : 2

Alcohol adding in the mixture = 10 litres

After adding water the ratio of mixture = 3 : 5

**Calculation:**

Let acid and alcohol in the mixture be 3x and 2x respectively

According to question

⇒ 3x/(2x + 10) = 3/5

⇒ 15x = 6x + 30

⇒ 9x = 30

⇒ x = 10/3

The quantity of acid in the mixture = 10/3 × 3

⇒ 10

**∴ The quantity of acid in the original solution is 10.**