3-7 Percent of ChangeObjective: Students find percents of increase and decrease and solve problems involving percents of change.

S. Calahan

2008

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

Find the Percent of Change

original: 25new: 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

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

25 1003(100) = 25x use cross products

300 = 25x

300 = 25x

Divide both sides by 25

300 = 25x 25 25 12 = xThe percent of increase is 12%.

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

= 2.8125 taxRound to nearest hundredth$2.81 tax + $45 = $47.81 total

Find amount after discount

sweater: $38discount: 35% offFind the discount price.

.35(38) = 13.30 savingsSubtract savings from original price

$38 – 13.30 = $24.70 discount price