Lesson Quiz

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Warm Up
Lesson Presentation
Lesson Quiz
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Warm Up 1. Find 30 of 40. 2. Find 28 of 60.
Solve for x. 3. 22 x(50) 4. 17.2
x(86) 5. 20 is what percent of 80? 6. 36 is
what percent of 30?
12
16.8
0.44
38
25
120
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Objective
Find percent increase and decrease.
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Vocabulary
percent change percent increase percent
decrease discount markup
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A percent change is an increase or decrease given
as a percent of the original amount. Percent
increase describes an amount that has grown and
percent decrease describes an amount that has be
reduced.
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Example 1A Finding Percent Increase and Decrease
Find each percent change. Tell whether it is a
percent increase or decrease.
From 8 to 10
Simplify the numerator.
Simplify the fraction.
0.25
25
Write the answer as a percent.
8 to 10 is an increase, so a change from 8 to 10
is a 25 increase.
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Helpful Hint
Before solving, decide what is a reasonable
answer. For Example 1A, 8 to 16 would be a 100
increase. So 8 to 10 should be much less than
100.
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Example 1B Finding Percent Increase and Decrease
Find the percent change. Tell whether it is a
percent increase or decrease.
From 75 to 30
Simplify the numerator.
Simplify the fraction.
0.6
Write the answer as a percent.
60
75 to 30 is a decrease, so a change from 75 to 30
is a 60 decrease.
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Check It Out! Example 1a
Find each percent change. Tell whether it is a
percent increase or decrease.
From 200 to 110
Simplify the numerator.
Simplify the fraction.
0.6
Write the answer as a percent.
60
200 to 110 is an decrease, so a change from 200
to 110 is a 60 decrease.
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Check It Out! Example 1b
Find each percent change. Tell whether it is a
percent increase or decrease.
From 25 to 30
Simplify the numerator.
Simplify the fraction.
0.20
Write the answer as a percent.
20
25 to 30 is an increase, so a change from 25 to
30 is a 20 increase.
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Check It Out! Example 1c
Find each percent change. Tell whether it is a
percent increase or decrease.
From 80 to 115
Simplify the numerator.
Simplify the fraction.
0.4375
Write the answer as a percent.
43.75
80 to 115 is an increase, so a change from 80 to
115 is a 43.75 increase.
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Example 2 Finding Percent Increase and Decrease
A. Find the result when 12 is increased by 50.
Find 50 of 12. This is the amount of increase.
0.50(12) 6
It is a percent increase, so add 6 to the
original amount.
12 6 18
12 increased by 50 is 18.
B. Find the result when 55 is decreased by 60.
Find 60 of 55. This is the amount of decrease.
0.60(55) 33
It is a percent decrease so subtract 33 from the
the original amount.
55 33 22
55 decreased by 60 is 22.
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Check It Out! Example 2
A. Find the result when 72 is increased by 25.
Find 25 of 72. This is the amount of increase.
0.25(72) 18
It is a percent increase, so add 18 to the
original amount.
72 18 90
72 increased by 25 is 90.
B. Find the result when 10 is decreased by 40.
Find 40 of 10. This is the amount of decrease.
0.40(10) 4
It is a percent decrease so subtract 4 from the
the original amount.
10 4 6
10 decreased by 40 is 6.
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Common application of percent change are
discounts and markups.
A discount is an amount by which an original
price is reduced.
A markup is an amount by which a wholesale price
is increased.
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Example 3 Discounts
The entrance fee at an amusement park is 35.
People over the age of 65 receive a 20 discount.
What is the amount of the discount? How much do
people over 65 pay?
Method 1 A discount is a percent decrease. So
find 35 decreased by 20.
Find 20 of 35. This is the amount of the
discount.
0.20(35) 7
35 7 28
Subtract 7 from 35. This is the entrance fee for
people over the age of 65.
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Example 3A Discounts
Method 2 Subtract the percent discount from 100.
People over the age of 65 pay 80 of the regular
price, 35.
100 20 80
0.80(35) 28
Find 80 of 35. This is the entrance fee for
people over the age of 65.
35 28 7
Subtract 28 from 35. This is the amount of the
discount.
By either method, the discount is 7. People over
the age of 65 pay 28.00.
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Example 3B Discounts
A student paid 31.20 for art supplies that
normally cost 52.00. Find the percent discount .
Think 20.80 is what percent of 52.00? Let x
represent the percent.
52.00 31.20 20.80
20.80 x(52.00)
Since x is multiplied by 52.00, divide both sides
by 52.00 to undo the multiplication.
0.40 x
Write the answer as a percent.
40 x
The discount is 40
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Check It Out! Example 3a
A 220 bicycle was on sale for 60 off. Find the
sale price.
Method 2 Subtract the percent discount from 100.
100 60 40
The bicycle was 60 off of 100 .
0.40(220) 88
Find 40 of 220. This is the discount from the
original price.
220 88 142
By this method, the discount is 88. The sale
price is 142.00.
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Check It Out! Example 3b
Ray paid 12 for a 15 T-shirt. What was the
percent discount ?
Think 3 is what percent of 15? Let x represent
the percent.
15 12 3
3 x(15)
Since x is multiplied by 15, divide both sides by
15 to undo the multiplication.
0.20 x
20 x
Write the answer as a percent.
The discount is 20.
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Example 4 Markups
The wholesale cost of a DVD is 7. The markup is
85. What is the amount of the markup? What is
the selling price?
Method 1
Method 2
A markup is a percent increase. So find 7
increased by 85.
Add percent markup to 100
Find 85 of 7. This is the amount of the markup.
The selling price is 185 of the wholesale price,
7.
100 85 185
0.85(7) 5.95
7 5.95 12.95
1.85(7) 12.95
Add to 7. This is the selling price.
Find 185 of 7. This is the selling price.
12.95 ? 7 5.95
Subtract from 12.95. This is the amount of the
markup.
By either method, the amount of the markup is
5.95. The selling price is 12.95.
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Check It Out! Example 4
A video game has a 70 markup. The wholesale cost
is 9. What is the selling price?
Method 1
A markup is a percent increase. So find 9
increased by 70.
Find 70 of 9. This is the amount of the markup.
0.70(9) 6.30
9 6.30 15.30
Add to 9. This is the selling price.
The amount of the markup is 6.30. The selling
price is 15.30.
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Check It Out! Example 4
What is the percent markup on a car selling for
21,850 that had a wholesale cost of 9500?
21,850 9,500 12,350
Find the amount of the markup.
Think 12,350 is what percent of 9,500? Let x
represent the percent.
12,350 x(9,500)
Since x is multiplied by 9,500 divide both sides
by 9,500 to undo the multiplication.
1.30 x
Write the answer as a percent.
130 x
The markup was 130 percent.