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