A retailer buys 40 pens at the marked price of 36 pens from a wholesaler. If he sells these pens giving a discount of 1 %, what is the profit percentage?

Correct option is D

Let's assume the marked price of each pen is Rs. 1. So,
the retailer buys 40 pens for Rs. 36.
Now, if the marked price of each pen is Rs. 1, then the selling price after a 1% discount will be:
Selling price of each pen = Marked price of each pen - Discount
Selling price of each pen = 1 - $$\frac1{100}$$​ = 0.99
Selling price of 40 pens = 40 $$\times$$​ 0.99 = Rs. 39.6
The cost price of 40 pens is Rs. 36. So,
Profit = Selling price - Cost price
Profit = 39.6 - 36 = Rs. 3.6
Profit % = $$\frac{3.6}{36} \times 100$$​ = 10%