Percent Increase and
Decrease
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Objectives
• Students will find percent increase.
• Students will find percent decrease.
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Vocabulary
• percent of change – when an increase or decrease
is expressed as a percent.
• percent increase – new amount is greater than the
original amount.
• percent decrease – new amount is smaller than the
original amount.
• discount – the amount by which the regular price is
reduced
• markup – the store sells the item for more than
they paid for the item.
• selling price – the amount the customer pays.
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Percent of Change
• To find the percent of change: Subtract the new
and original amount. Divide the answer by the
ORIGINAL amount.
• To find a percent discount, change the percent
to a decimal and multiply by the original amount.
SUBTRACT this number from the original
amount.
• To find a markup, change the percent to a
decimal and multiply by the original amount.
ADD this number to the original amount.
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Percent of Change
• To find the percent of change: Subtract
the new and original amount. Divide
the answer by the ORIGINAL amount.
New – original
original
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Example 1
• Find the percent of change. Round to the
nearest percent.
• Original: 53
• New: 61
• 61 – 53 = 8
• 8 ÷ 53 = .15 = 15%
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Example 2
• Find the percent of change. Round to the
nearest percent.
• Original: 65
• New: 40
• 40 – 65 = -25
• -25 ÷ 65 = .38 = -38%
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Example 3
• Find the percent of change. Round to the
nearest percent.
• Original: $45
• New: $25
• 25 – 45 = - 20
• -20 ÷ 45 = .44 = 44%
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Practice
• Round to the nearest percent.
• Original: $55; new: $35
• Original: $120; new $85
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Practice:
Sales The price a used-book store pays to buy a
book is $5. The store sells the book for 28% above
the price that it pays for the book. What is the selling
price of the $5 book?
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Practice:
Sales The price a used-book store pays to buy a
book is $5. The store sells the book for 28% above
the price that it pays for the book. What is the selling
price of the $5 book?
5 x 0.28 = $1.40
5 + 1.40 = $6.40
OR
5 x 1.28 = $6.40
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Practice:
At one store the price of a pair of jeans is $26.00. At
another store the same pair of jeans has a price that
is 22% higher. What is the price of jeans at the
second store?
Answer: The price of jeans at the second store is
$31.72.
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Practice:
Sales Tax A meal for two at a restaurant costs
$32.75. If the sales tax is 5%, what is the total price
of the meal?
Answer: The total price of the meal is $34.49.
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Practice:
A portable CD player costs $69.99. If the sales tax is
6.75%, what is the total price of the CD player?
Answer: The total price of the CD player is $74.71.
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Practice:
Discount A dog toy is on sale for
20% off the original price. If the
original price of the toy is $3.80,
what is the discounted price?
Answer: The discounted price of the dog
toy is $3.04.
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Practice:
A baseball cap is on sale for 15% off the original
price. If the original price of the cap is $19.99, what
is the discounted price?
Answer: The discounted price of the cap player is
$16.99.
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