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8.5 Problem Solving Using Percent
You can use percents to solve real life problems, such as interpreting circle graphs or finding discounts.
Example In a survey conducted
by a local newspaper, adults were asked how many hours per week they spent exercising. Suppose 18 adults said they spent 7 or more hours per week.
Weekly Exercise Time
0 hours
45%
1-3 hr
33%
4-6 hours
17%
5%7 or more hours
Example - continued How many adults were
surveyed? Think…..What
information do we have?18 people said they
exercised for 7+ hours.That is 5% of the total. How would that be
written in the “is-of” statement?
18 is 5% of what number?
x adults360
18 5100x
5 1800x 5 5
Example - continued How many adults said 0
hours? Again…what do we know?
45% said they exercised for 0 hours.
There are a total of 360 adults How would that be written
in the “is-of” statement?
What number is 45% of 360?
x360
45100
100 16200x 100 100
x adults162
Discount Last weekend you
bought a jacket on sale for $63.75. Today you are shopping in the same store and notice that the jacket is being sold at the regular price of $75. What was the discount percent you received last weekend?
amount of discountoriginal price
%
100
75 63 7575 100
. x
11 2575 100.
x
75 75
75 1125x
x 15%
Increase or Decrease A percent of increase or percent of
decrease tells how much a quantity has changed.
The percent of change of a quantity is given by
actual changeoriginal amount
Examples 1995 profits - $235,000 1996 profits - $455,000 Find the percent of increase
members in 1996 – 422 members in 1997 – 394 Find the percent of
decrease455 000 235 000
235 000220 000235 000
, ,,
,,
x 94%
28442 100
x
x 7%
422 394422
28422
220 000235 000 100
,,
x