6-4 Percent of Change
Percent of change =
amount of change
original amount
6-4 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.
65 is decreased to 38.
Find the amount of change.
65 – 38 = 27
Substitute values into
percent of change = 27
formula.
65
 0.4153846 Divide.
 41.5%
Write as a percent. Round.
The percent of decrease is about 41.5%.
Helpful Hint
When a number is decreased, subtract the new
amount from the original amount to find the
amount of change.
6-4 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.
41 is increased to 92.
92 – 41 = 51 Find the amount of change.
Substitute values into
51
Percent of change =
41 formula.
Divide.
 1.2439
 124.4% Write as a percent. Round.
The percent of increase is about 124.4%
Helpful Hint
When a number is increased, subtract the
original amount from the new amount.
6-4 Percent of Change
Check It Out: Example 1A
Find the percent of change. Round answers to
the nearest tenth of a percent, if necessary.
70 is decreased to 45.
70 – 45 = 25
percent of change = 25
70
Find the amount of change.
Substitute values into
formula.
 0.35714
Divide.
 35.7%
Write as a percent. Round.
The percent of decrease is about 35.7%.
6-4 Percent of Change
Check It Out: Example 1B
Find the percent of change. Round answers to
the nearest tenth of a percent, if necessary.
37 is increased to 56.
56 – 37 = 19 Find the amount of change.
Substitute values into
Percent of change = 19
37 formula.
 0.51351
Divide.
 51.4%
Write as a percent. Round.
The percent of increase is about 51.4%
6-4 Percent of Change
When you know the percent of change, you can
use an equation to find the actual amount of
change.
6-4 Percent of Change
Additional Example 2: Using Percent of Change
The regular price of a bicycle helmet is $42.99.
It is on sale for 20% off. What is the sales
price?
Step 1: Find the amount of the discount d.
20% · 42.99 = d Think: 20% of $42.99 is what number?
0.20 · 42.99 = d Write the percent as a decimal.
8.598 = d Multiply.
$8.60  d Round to the nearest cent.
The amount of the discount is $8.60.
6-4 Percent of Change
Additional Example 2 Continued
The regular price of a bicycle helmet is $42.99.
It is on sale for 20% off. What is the sales
price?
Step 2: Find the sale price.
regular price – amount of discount = sales price
$42.99
–
$8.60
The sale price is $34.39
=
$34.39
6-4 Percent of Change
Check It Out: Example 2
The regular price of a computer game is $49.88.
It is on sale for 15% off. What is the sales price?
Step 1: Find the amount of the discount d.
15% · 49.88 = d Think: 15% of $49.88 is what number?
0.15 · 49.88 = d Write the percent as a decimal.
7.482 = d Multiply.
$7.48  d Round to the nearest cent.
The amount of the discount is $7.48.
6-4 Percent of Change
Check It Out: Example 2 Continued
The regular price of a computer game is $49.88.
It is on sale for 15% off. What is the sales price?
Step 2: Find the sale price.
regular price – amount of discount = sales price
$49.88
–
$7.48
The sale price is $42.40.
=
$42.40
6-4 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 retail price of
the T-shirts?
Step 1: Find the actual amount of increase.
Think: 110% of $12.60 is what number?
110% · 12.60 = n
1.10 · 12.60 = n Write the percent as a decimal.
13.86 = n Multiply.
Step 2: Find the selling price.
wholesale price + amount of increase = retail price
$12.60
+
$13.86
=
$26.46
The retail price of the hand-painted T-shirts is $26.46 each.
6-4 Percent of Change
Check It Out: Example 3
William makes T-shirts for $7.00 each and
sells them after a price increase of 125%.
What is the retail price of the T-shirts?
Step 1: Find the actual amount of increase.
Think: 125% of $7.00 is what number?
125% · 7.00 = n
1.25 · 7.00 = n
8.75 = n
Write the percent as a decimal.
Multiply.
Step 2: Find the selling price.
wholesale price + amount of increase = retail price
$7.00
+
$8.75
=
$15.75
The retail price of the T-shirts is $15.75 each.
6-4 Percent of Change
Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems
6-4 Percent of Change
Lesson Quiz
Find each percent of change.
1. 10 is increased to 12. 20%
2. 25 is increased to 45. 80%
3. 10 is decreased to 1. 90%
4. The regular price of a coat is $120. It is on sale
$90
for 25% off. What is the sale price?
5. A backpack that sells for $42 is on sale for
25% off. Find the sale price.
$31.50
6-4 Percent of Change
Lesson Quiz for Student Response Systems
1. Identify the percent of change.
20 is increased to 22.
A. 10%
B. 20%
C. 30%
D. 40%
6-4 Percent of Change
Lesson Quiz for Student Response Systems
2. Identify the percent of change.
30 is increased to 54.
A. 30%
B. 54%
C. 75%
D. 80%
6-4 Percent of Change
Lesson Quiz for Student Response Systems
3. Identify the percent of change.
15 is decreased to 3.
A. 80%
B. 75%
C. 60%
D. 50%
6-4 Percent of Change
Lesson Quiz for Student Response Systems
4. The regular price of a camera is $140. A
store offers 30% off on cameras. At this
discounted rate, what is the sale price of a
camera?
A. $110
B. $105
C. $98
D. $42
6-4 Percent of Change
Lesson Quiz for Student Response Systems
5. A camcorder that sells for $256 is on sale
for 30% off. Identify the sale price.
A. $195.60
B. $179.20
C. $106.40
D. $76.80