Author: Kathy Halverson
Last saved by: Glencoe Mathematics
Company: Halverson Household

Lesson 6-9

Example 1	Find Percent of Change
Find the percent of change from $32 to $44.

Step 1	Subtract to find the amount of change.
	44 - 32 = 12	new amount - original amount

Step 2	Write a ratio that compares the amount of change to the original amount. Express the ratio as a percent.

percent of change = 
		     	           = 			Substitution
		     	           = 0.375 or 37.5%	Write the decimal as a percent.

The percent of change from $32 to $44 is 37.5%.

Example 2	Find Percent of Increase
TEMPERATURE	In Cleveland, Ohio, the high temperature on one day was 43° F and the next day was 71° F.  Find the percent of change.

Step 1	Subtract to find the amount of change.
	71 - 43 = 28

Step 2	Write a ratio that compares the amount of change to the original temperature. Express the ratio as a percent.
percent of change = 
		           = 			Substitution
		     	           ≈ 0.65 or 65%		Write the decimal as a percent.

The percent of change is 65%. In this case, the percent of change is a percent of increase.

Example 3	Multiple-Choice Test Item
Refer to the table shown.   Which student had the greatest percent of increase in test score from pretest to posttest?

Student Name | Pretest Score | Posttest Score
Alex | 75 | 83
Emily | 84 | 89
Zachary | 63 | 91
Karli | 88 | 95

A  Alex		B  Emily		C  Zachary		D  Karli	

Read the Test Item
Percent of increase in test score tells how much the test score has increased in relation to the pre-test score.

Solve the Test Item
Use a ratio to find each percent of increase.  Then compare the percents.
• Alex						• Emily 
     =  				    = 
                  ≈ 0.107 or 10.7%			                 ≈ 0.06 or 6%

• Zachary					• Karli
    =  				    =  
     ≈ 0.444 or 44.4%			                 ≈ 0.08 or 8%

Zachary had the greatest percent of increase in test score.  The answer is C.

Example 4	Find Percent of Decrease
ENROLLMENT	In 1998, Redview Elementary School had 418 students enrolled and in 1999, there were 354 students enrolled.  What was the percent of change?

Step 1	Subtract to find the amount of change.
	354 - 418 = -64

Step 2	Compare the amount of change to the 1998 enrollment.
percent of change = 
		     	           = 			Substitution
		     	           ≈ -0.153 or –15.3%	Write the decimal as a percent.
The percent of change is -15.3%. In this case, the percent of change is a percent of decrease.