Correct Answer - Option 2 : 10%

**Given**

A book is listed at Rs 150, with a discount of 20%

**Formula used**

MP(1 - D/100) = SP

MP = Marked price

D = Discount

SP = Selling price

**Calculation**

Marked price = 150

⇒ Cost = 150 (1 - 20/100)

⇒ Cost = 150 × 80/100 = 120

⇒ Let additional discount be x%

⇒ 120 - 108 = 12

⇒ x% of 120 = 12

⇒ x = (12 × 100)/120

⇒ x = 10

**∴ Additional discount is 10%**