Percent Increase and
Decrease
Lesson 6-4
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Percent of In
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Percents are often used to
describe changes .
Percent change is the ratio of the amount of
change to the original amount.
percent change = amount of change original amount
Percent increase
describes how
much the original
amount increases.
Percent decrease
describes how
much the original
amount decreases.
Subtract the two numbers in the problem.
Subtract the two numbers in the problem.
Set up a ratio
amount of change
original amount
Subtract the two numbers in the problem.
Set up a ratio
amount of change
original amount
Divide the ratio to get a decimal.
Subtract the two numbers in the problem.
Set up a ratio
amount of change
original amount
Divide the ratio to get a decimal.
Convert the decimal to a percent. Move the decimal 2 places right.
45 - 36 = 9
First find the amount of change.
45 - 36 = 9
First find the amount of change.
amount of increase original amount
45 - 36 = 9
Set up the ratio.
First find the amount of change.
amount of increase original amount
9 = 0.25 = 25%
36
9 36
9 36
Set up the ratio.
Find the decimal form and
write it as a percent.
45 - 36 = 9
First find the amount of change.
amount of increase original amount
9 = 0.25 = 25%
36
9 36
Set up the ratio.
Find the decimal form and
write it as a percent.
From 36 to 45 is a 25% increase.
Find the percent of change from 372 to 186.
Subtract biggest minus smallest.
amount of change
original amount
Divide the fraction to get a decimal.
Dr. Pepper
(Decimal to Percent)
465 - 372 = 93
93
372
.25
.25 = 25%
Find the percent of change from 372 to 186.
Subtract biggest minus smallest.
amount of change
original amount
Divide the fraction to get a decimal.
Dr. Pepper
(Decimal to Percent)
372 - 186 = 186
93
372
.25
.25 = 25%
Find the percent of change from 372 to 186.
Subtract biggest minus smallest.
amount of change
original amount
Divide the fraction to get a decimal.
Convert
(Decimal to Percent)
372 - 186 = 186
186
372
.5
.50 = 50%
decrease
Find the percent of change from 372 to 186.
Subtract biggest minus smallest.
amount of change
original amount
Divide the fraction to get a decimal.
Dr. Pepper
(Decimal to Percent)
372 - 186 = 186
186
372
.5
.25 = 25%
Find the percent of change from 372 to 186.
Subtract biggest minus smallest.
amount of change
original amount
Divide the fraction to get a decimal.
Dr. Pepper
(Decimal to Percent)
372 - 186 = 186
186
372
.5
.50 = 50%
decrease
You Try It Now
originally: $300
50%
Answer
new price: $450
_________ % increase
originally: $2500
67
Answer
new price: $825
_________ % decrease
The heart rate of a grizzly bear slows from 50 to 8 beats per minute during hibernation. What is the percent decrease?
84%
Answer
Click
Remember
% change = amount of change original amount
Ben has 765 cards in his baseball card collection.
He sells 153 of the cards. What is the percent of
decrease in the number of cards in the collection?
20%
Click
Using Percent Increase or Decrease to Find Prices
Anthony bought a lap top computer originally
priced at $750 that was reduced in price by
35%. What was the reduced price?
$750 x 35%
First find 35% of $750
$750 x 0.35 = $262.50
The amount of decrease is $262.50.
$750 ­ $262.50 = $487.50.
Subtract the amount
of decrease.
The reduced price of the lap top was $487.50.
Homework
Test
Worksheet 3.2
(Both Sides)
Friday
December 9