A book normally costs $21.50. today it was on sale for 15.05. what percentage discount was offered during the sale?

To find the discount %, we must use the equation below.

Discounted Price / Original Price = 1 - Discount %

15.05 / 21.5 = 1 - Discount %

Subtract 15.05 / 21.5 from both sides and add Discount % to both sides to get the following equation.

Discount % = 1 - 15.05 / 21.5 = 1 - 0.7 = 0.3 = 30% discounted