The selling price of 15 items equals the cost of 20 items. What is the percentage profit earned by the seller?

Question: The selling price of 15 items equals the cost of 20 items. What is the percentage profit earned by the seller?

Solution:
Cost Price of 20 items = Selling Price of 15 items

Let,
Cost Price of each item = 1

Then,
Cost Price of 20 items = 20
And
Selling Price of 15 items = 20
∴ Selling Price of 1 item = 20/15 = 4/3

∴ Profit % = [{(4/3) - 1}/1] × 100%
= (1/3) × 100
= 33.33%