Using percentages for expressing discounts and comparing prices

Discounts

Question 1

A shoe shop has a sale.

Original price was $95 Sale price is 20% off	Original price was $90 Sale price is 25% off

What is the difference in sale price of the two pairs of shoes?

Solution

Method 1

For the pair on the left:
Sale price = original price − discount.
20% = $\dfrac{20}{100}$ = 0.2.
Sale price for the first pair	= $95 − 20% × $95 (This can be typed directly into the calculator.)
	= $95 − (0.2 × $95)
	= $76.

For the pair on the right:
25% = $\dfrac{25}{100}$ = 0.25.
Sale price for the second pair	= $90 − 25% × $90
	= $90 − (0.25 × $90)
	= $67.50.

The difference between the sale prices is = $76 − $67.50 = $8.50.

Method 2

© Australian Mathematical Sciences Institute, except where indicated otherwise. This material is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported (CC BY-NC 3.0) licence http://creativecommons.org/licenses/by-nc/3.0/

For the pair on the left:
Sale price = original price − discount.
20% = \(\dfrac{20}{100}\) = 0.2.
Sale price for the first pair	= $95 − 20% × $95 (This can be typed directly into the calculator.)
	= $95 − (0.2 × $95)
	= $76.

For the pair on the right:
25% = \(\dfrac{25}{100}\) = 0.25.
Sale price for the second pair	= $90 − 25% × $90
	= $90 − (0.25 × $90)
	= $67.50.