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Warm Up 1. 14,000 is 2 % of what number? 2. 39 is 13% of what number?

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1

1

2

2

Warm Up

1.14,000 is 2 % of what number?

2. 39 is 13% of what number?

3. 37 % of what number is 12?

4. 150% of what number is 189?

560,000

300

32

126

Problem of the Day

In a school survey, 45% of the students said orange juice was their favorite juice, 25% preferred apple, and 10% preferred grapefruit. The remaining 32 students preferred grape juice. How many students participated in the survey?

160 students

Learn to find percent increase and decrease.

amount of change

original amount

=

percent decrease

100

Percent decrease describes how much the original amount decreases.

4

16

amount of decrease

original amount

Additional Example 1: Finding Percent Increase or Decrease

Find the percent increase or decrease from 16 to 12.

This is percent decrease.

16 – 12 = 4First find the amount of change.

Think: What percent is 4 of 16?

Set up the ratio.

4

16

Additional Example 1 Continued

= 0.25Find the decimal form.

= 25%Write as a percent.

From 16 to 12 is a 25% decrease.

5

20

amount of increase

original amount

Check It Out: Example 1

Find the percent increase or decrease from 15 to 20.

This is percent increase.

20 – 15 = 5First find the amount of change.

Think: What percent is 5 of 20?

Set up the ratio.

5

20

Check It Out: Example 1 Continued

= 0.25Find the decimal form.

= 25%Write as a percent.

From 15 to 20 is a 25% increase.

28

70

amount of increase

original amount

Additional Example 2A: Life Science Application

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 = 28First find the amount of change.

Think: What percent is 28 of 70?

Set up the ratio.

28

70

= 0.4Find the decimal form.

Additional Example 2 Continued

= 40%Write as a percent.

Jim’s heart rate increased by 40% when he exercised.

amount of decrease

0.40

original amount

1.25

Additional Example 2B: Application

In 1999, a certain stock was worth $1.25 a share. In 2002, the same stock was worth $0.85 a share. What was the percent decrease?

1.25 – 0.85 = 0.40First find the amount of change.

Think: What percent is 0.40 of 1.25?

Set up the ratio.

0.40

1.25

Additional Example 2B Continued

= 0.32Find the decimal form.

= 32%Write as a percent.

The value of the stock decreased by 32%.

25

50

amount of increase

original amount

Check It Out: Example 2A

When Jeff was watching TV, the number of times his eyelids blinked went from 50 blinks per minute to 75 blinks per minute. What was the percent increase?

75 – 50 = 25First find the amount of change.

Think: What percent is 25 of 50?

Set up the ratio.

25

50

= 0.5Find the decimal form.

Check It Out: Example 2A Continued

= 50%Write as a percent.

The blinking of Jeff’s eyelids increased by 50% when he watched TV.

amount of decrease

5.20

original amount

9.00

Check It Out: Example 2B

In 2000, a certain stock was worth $9.00 a share. In 2003, the same stock was worth $3.80 a share. What was the percent decrease, to the nearest tenth?

9.00 – 3.80 = 5.20First find the amount of change.

Think: What percent is 5.20 of 9.00?

Set up the ratio.

5.20

= 0.57Find the decimal form.

9.00

= 57.7%Write as a percent.

Check It Out: Example 2B Continued

The value of the stock decreased by about 57.8%.

Additional Example 3A: Using Percent Change to Find Discounts and Markups

Sarah bought a DVD player originally priced at $450 that was on sale for 20% off. What was the sale price?

$450 20%First find 20% of $450.

$450 0.20 = $9020% = 0.20

The amount of decrease is $90.

Think: The reduced price is $90 less than $450.

$450 – $90 = $360Subtract the amount of decrease.

The sale price of the DVD player was $360.

Additional Example 3B: Using Percent Change to Find Discounts and Markups

Mr. Olsen has a computer business in which he marks everything up 40% above the wholesale price. If he purchased a printer for $85 wholesale, what will be the retail price?

$85 40% First find 40% of $85.

$85 0.40 = $3440% = 0.40

The amount of increase is $34.

Think: The retail price is $34 more than $85.

$85 + $34 = $119Add the amount of increase.

The retail price of this printer will be $119.

Check It Out: Example 3A

Lily bought a dog house originally priced at $750 that was on sale for 10% off. What was the sale price?

$750 10%First find 10% of $750.

$750 0.10 = $7510% = 0.10

The amount of decrease is $75.

Think: The reduced price is $75 less than $750.

$750 – $75 = $675Subtract the amount of decrease.

The sale price of the dog house was $675.

Check It Out: Example 3B

Barb has a grocery store in which she sells everything at 50% above the wholesale price. If she purchased a prime rib for $30 wholesale, what will be the retail price?

$30 50% First find 50% of $30.

$30 0.50 = $1550% = 0.50

The amount of increase is $15.

Think: The retail price is $15 more than $30.

$30 + $15 = $45Add the amount of increase.

The retail price of the prime rib will be $45.

Lesson Quizzes

Standard Lesson Quiz

Lesson Quiz for Student Response Systems

Lesson Quiz

Find each percent increase or decrease to the nearest percent.

1. from 12 to 15

2. from 1625 to 1400

3. from 37 to 125

4. from 1.25 to 0.85

5. A computer game originally sold for $40 but is now on sale for 30% off. What is the sale price of the computer game?

25% increase

14% decrease

238% increase

32% decrease

$28

Lesson Quiz for Student Response Systems

1. Identify the percent increase or decrease to the nearest percent.

from 23 to 29

A. 26% decrease

B. 26% increase

C.32% decrease

D.32% increase

Lesson Quiz for Student Response Systems

2. Identify the percent increase or decrease to the nearest percent.

from 1440 to 1220

A. 15% decrease

B. 15% increase

C.28% decrease

D. 28% increase

Lesson Quiz for Student Response Systems

3. A winter coat originally sold for $75 but is now on sale for 20% off. What is the sale price of the winter coat?

A. $55

B. $60

C. $65

D. $70