DRDO Multi tasking staff Model paper 9

Cost price of calculator = Rs. 400
Marked price = 400 + 37.5% of 400 = 400 + 3/8 × 400 = 400 + 150 = Rs. 550
Discount of 10% = 10% of 550 = 1/10 × 550 = Rs. 55
Additional discount = Rs. 15
⇒ Selling price = 550 - 55 - 15 = Rs. 480
∴ Profit earned by shopkeeper = 480 - 400 = Rs. 80