LESSON
Percent Increase and Decrease
6-5
Lesson Objectives
Find percent increase and decrease
Vocabulary
percent change (p. 294)
percent increase (p. 294)
percent decrease (p. 294)
Additional Examples
Example 1
Find the percent increase or decrease from 16 to 12.
This is percent decrease.
16 12 First find the amount of
Think: What percent is
amount of decrease
original amount
of 16?
16
4
16
.
Set up the ratio.
Find the decimal form.
%
From 16 to 12 is a
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Write as a percent.
%
.
124
Holt Mathematics
LESSON
Percent Increase and Decrease
6-5
Lesson Objectives
Find percent increase and decrease
Vocabulary
percent change (p. 294) The ratio of the amount of change to the original
amount.
percent increase (p. 294) A percent change that describes how much the
original amount increases.
percent decrease (p. 294) A percent change that describes how much the
original amount decreases.
Additional Examples
Example 1
Find the percent increase or decrease from 16 to 12.
This is percent decrease.
16 12 4
First find the amount of change
Think: What percent is 4
amount of decrease
original amount
4
0.25
16
25
.
of 16?
4
16
Set up the ratio.
Find the decimal form.
%
From 16 to 12 is a 25
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Write as a percent.
% decrease
124
.
Holt Mathematics
LESSON 6-5 CONTINUED
Example 2
A. When Jim was exercising, his heart rate went from 70 beats per
minute to 98 beats per minute. What was the percent increase?
98 70 First find the amount of change.
Think: What percent of 28 is 70?
amount of increase
original amount
Set up the ratio.
%
Find the decimal form. Write as a percent.
Jim’s heart rate
by
% when he was exercising.
Example 3
A. Sarah bought a DVD player originally priced at $450 that was on sale
for 20% off. What was the sale price?
$450
20%
$450
0.
First find
$
The amount of decrease is $
Think: The reduced price is $
$450 $
$
% of $450.
20% 0.
.
less than $450.
Subtract the amount of decrease.
The sale price of the DVD player was $
.
Try This
1. Find the percent increase or decrease from 15 to 20.
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
125
Holt Mathematics
LESSON 6-5 CONTINUED
Example 2
A. When Jim was exercising, his heart rate went from 70 beats per
minute to 98 beats per minute. What was the percent increase?
98 70 28
First find the amount of change.
Think: What percent of 28 is 70?
28
amount of increase
original amount
Set up the ratio.
70
28
0.4
40
%
Find the decimal form. Write as a percent.
70
Jim’s heart rate increased
by 40
% when he was exercising.
Example 3
A. Sarah bought a DVD player originally priced at $450 that was on sale
for 20% off. What was the sale price?
$450
20%
$450
0.
20
First find 20
$ 90
The amount of decrease is $ 90
Think: The reduced price is $ 90
$450 $ 90
$ 360
% of $450.
20% 0. 20
.
less than $450.
Subtract the amount of decrease.
The sale price of the DVD player was $ 360
.
Try This
1. Find the percent increase or decrease from 15 to 20.
1
333% increase
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
125
Holt Mathematics