The percent that a value

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Percent of Change

• The percent that a value
• increases or decreases

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Vocabulary (Section 5.7 in book)

• A percent of change is
• a ratio that compares the change in a quantity
  to the original amount.

• For a percent of change, the proportion used is

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Ex 1) The Mitchell family bought a house several
years ago for 120,000. This year, they sold it
for 150,000. Find the percent of increase in
the price of the house.
A percent of increase is a percent of change.
Subtract the house values to find the amount of
change.
Use the starting price as the original amount.
The price of the house increased by 25.
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Ex 2) Mercer Middle School had 240 students last
year. This year, there are 192 students
enrolled. Find the percent of change in the
number of students. Is this a percent increase
or a percent decrease?
The percent of change is a percent of decrease.
Subtract the number of students to find the
amount of change.
Use the earlier number of students as the
original amount.
The number of students decreased by 20.
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Ex 3) The average speed of the winning race cars
in the Indy 500 are shown in the table. Find the
percent of change in speed from 1955 to 2010.
Round your answer to the nearest whole percent.
Year Speed (mph)
1922 94
1955 128
2010 162
The percent of change is a percent of increase.
Subtract the speeds between 1955 and 2010 to find
the amount of change.
Use the average speed from 1955 as the original
amount.
The average speed increased by approximately 27.