1. 6-5 Percent of Change Warm Up Problem of the Day Lesson Presentation
Course 2
Warm Up
Problem of the Day
Lesson Presentation

2. 6-5 Percent of Change Warm Up Solve. 1. 10% of what number is 6?
Course 2
6-5
Percent of Change
Warm Up
Solve.
1. 10% of what number is 6?
2. What percent of 20 is 8?
3. What is 80% of 60?
4. 50 is what percent of 200? 60
40% 48
25%

3. 6-5 Percent of Change Problem of the Day
Course 2
6-5
Percent of Change
Problem of the Day
A pair of $100 sneakers was on sale for 50% off. Then the store manager marked them down another 30%. She then discounted the price by 20%. What is the total discount as a percent of the original price?
72%

4. Course 2
6-5
Percent of Change
Learn to solve problems involving percent of change.

5. Insert Lesson Title Here
Course 2
6-5
Percent of Change
Insert Lesson Title Here
Vocabulary
percent of change
percent of increase
percent of decrease

6. Course 2
6-5
Percent of Change
A percent can be used to describe an amount of change. The percent of change is the amount, stated as a percent, that a number increases or decreases. If the amount goes up, it is a percent of increase. If the amount goes down, it is a percent of decrease.
You can find the percent of change by using the following formula.
amount of change
original amount
Percent of change =

7. Additional Example 1A: Finding Percent of Change
Course 2
6-5
Percent of Change
Additional Example 1A: Finding Percent of Change
Find the percent of change. Round answers to the nearest tenth of a percent, if necessary.
A. 65 is decreased to 38.
Find the amount of change.
65 – 38 = 27 27 65
Substitute values into
formula.
percent of change = 
Divide.
 41.5%
Write as a percent. Round.
The percent of decrease is about 41.5%.
When a number is decreased, subtract the new amount from the original amount to find the amount of change.
Helpful Hint

8. Additional Example 1B: Finding Percent of Change
Course 2
6-5
Percent of Change
Additional Example 1B: Finding Percent of Change
Find the percent of change. Round answers to the nearest tenth of a percent, if necessary.
B. 41 is increased to 92.
92 – 41 = 51
Find the amount of change. 41 51
Substitute values into
formula.
Percent of change = 
Divide.
 124.4%
Write as a percent. Round.
The percent of increase is about 124.4%
When a number is increased, subtract the original amount from the new amount.
Helpful Hint

9. 6-5 Percent of Change Try This: Example 1A
Course 2
6-5
Percent of Change
Try This: Example 1A
Find the percent of change. Round answers to the nearest tenth of a percent, if necessary.
A. 70 is decreased to 45.
Find the amount of change.
70 – 45 = 25 25 70
Substitute values into
formula.
percent of change = 
Divide.
 35.7%
Write as a percent. Round.
The percent of decrease is about 35.7%.

10. 6-5 Percent of Change Try This: Example 1B
Course 2
6-5
Percent of Change
Try This: Example 1B
Find the percent of change. Round answers to the nearest tenth of a percent, if necessary.
B. 37 is increased to 56.
56 – 37 = 19
Find the amount of change. 37 19
Substitute values into
formula.
Percent of change = 
Divide.
 51.4%
Write as a percent. Round.
The percent of increase is about 51.4%

11. Course 2
6-5
Percent of Change
When you know the percent of change, you can use an equation to find the actual amount of change.

12. Additional Example 2A & 2B: Using Percent of Change
Course 2
6-5
Percent of Change
Additional Example 2A & 2B: Using Percent of Change
The regular price of a bicycle helmet is $ It is on sale for 20% off.
A. Find the actual amount of the discount.
20% · = d
Think: 20% of $42.99 is what number?
0.20 · = d
Write the percent as a decimal.
8.598 = d
Multiply.
$8.60  d
Round to the nearest cent.
The discount is $8.60.
B. Find the sale price.
Subtract the discount from the regular price.
$42.99 – $8.60 = $34.39
The sale price is $34.39

13. 6-5 Percent of Change Try This: Example 2A & 2B
Course 2
6-5
Percent of Change
Try This: Example 2A & 2B
The regular price of a computer game is $ It is on sale for 15% off.
A. Find the actual amount of the discount.
15% · = d
Think: 15% of $49.88 is what number?
0.15 · = d
Write the percent as a decimal.
7.482 = d
Multiply.
$7.48  d
Round to the nearest cent.
The discount is $7.48.
B. Find the sale price.
Subtract the discount from the regular price.
$49.88 – $7.48 = $42.40
The sale price is $42.40

14. Additional Example 3: Business Application
Course 2
6-5
Percent of Change
Additional Example 3: Business Application
A boutique buys hand-painted T-shirts for $12.60 each and sells them at a 110% increase in price. What is the selling price of the T-shirts?
First find the actual amount of increase.
Think: 110% of $12.60 is what number?
110% · = n
1.10 · = n
Write the percent as a decimal.
13.86 = n
Multiply.
The amount of increase is $ Now find the selling price.
Think: retail price = wholesale price + amount of increase.
p = $ $13.86
p = $26.46
The retail price of the hand-painted T-shirts is $26.46 each.

15. Insert Lesson Title Here
Course 2
6-5
Percent of Change
Insert Lesson Title Here
Try This: Example 3
William makes T-shirts for $7.00 each and sells them after a price increase of 125%. What is the selling price of the T-shirts?
First find the actual amount of increase.
Think: 125% of $7.00 is what number?
125% · 7.00 = n
1.25 · 7.00 = n
Write the percent as a decimal.
8.75 = n
Multiply.
The amount of increase is $8.75. Now find the selling price.
Think: retail price = wholesale price + amount of increase.
r = $ $8.75
r = $15.75
The retail price of the T-shirts is $15.75 each.

16. Insert Lesson Title Here
Course 2
6-5
Percent of Change
Insert Lesson Title Here
Lesson Quiz
Find each percent of change.
1. 10 is increased to 12.
2. 25 is increased to 45.
3. 10 is decreased to 1.
is decreased to 90.
5. A backpack that sells for $42 is on sale for % off. Find the amount of discount and the sale price.
20%
80%
90%
25%
$10.50, $31.50