1. 3-7 Percent of Change
Objective: Students find percents of increase and decrease and solve problems involving percents of change.
S. Calahan
2008

2. Percent of change
When an increase or decrease is expressed as a percent
Percent of increase – when the new number is greater than the original number
Percent of decrease – when the new number is less than the original

3. Find the Percent of Change
original: 25
new: 28
This is an increase because the new is greater than the original
To find the change subtract the largest from the smallest amount 28 – 25 = 3

4. original: 25 new: 28
28 – 25 = 3
Find the percent using the original number 25 as the base.
3 = x to find the percent set x over 100
3(100) = 25x use cross products
300 = 25x

5. 300 = 25x Divide both sides by 25 300 = 25x 25 25 12 = x
12 = x
The percent of increase is 12%.

6. Find Sales Tax
A concert ticket costs $45. If the sales tax is 6.25%, what is the total price of a ticket?
6.25% of $45 = .0625(45) of means times
= tax
Round to nearest hundredth
$2.81 tax + $45 = $47.81 total

7. Find amount after discount
sweater: $38
discount: 35% off
Find the discount price.
.35(38) = savings
Subtract savings from original price
$38 – = $24.70 discount price