7th Grade Math

Find Percent of Change

GASOLINE Find the percent of^1970

2008

$ 1 .3 0

GAS

$

3 .9^5

GAS

change in the cost of gasoline from

1970 to 2008. Round to the nearest

whole percent if necessary. Then

state whether the percent of change

is an increase or decrease.

Step 1 Find the amount of change.

$3.95 - $1.30 = $2.65

Step 2 Find the percent of change.

percent of change =

amount of change

__

original amount

= _$2.65

$1.30

Substitution

≈ 2.04 Simplify.

≈ 204% Write 2.04 as a percent.

The percent of change is 204%. Since the percent of change is

positive, this is a percent of increase.

DVD RECORDER Yusuf bought a DVD recorder for $280. Now, it is

on sale for $220. Find the percent of change in the price. Round

to the nearest whole percent if necessary. Then state whether the

percent of change is an increase or decrease.

Step 1 Find the amount of change.

$220 - $280 = -$60

Step 2 Find the percent of change.

percent of change =

amount of change

__

original amount

= _-$60

$280

Substitution

≈ -0.21 Simplify.

≈ -21% Write -0.21 as a percent.

The percent of change is -21%. Since the percent of change is

negative, this is a percent of decrease.

a. MEASUREMENT Find the percent of change from 10 yards to

13 yards. Then state whether the percent of change is an increase

or decrease.

b. MONEY Find the percent of change from $20 to $15. Then state

whether the percent of change is an increase or decrease.

Percents Percents

In the percent of change

formula, the decimal

repesenting the percent of

change must be written as

a percent.

Lesson 3B Applying Percents 347

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