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%