Download 7.3A Percent Involving Word Problems

7.3A Percent Involving Word Problems
To solve problems involving
percent
Use proportions or the decimal
equivalent of the percent to solve
a problem involving a percent.
Use a proportion to find a percent
in a word problem
#
x

; # is the unknown
total 100
percent, x/100 is the percent
expressed as a ratio (x per 100 or
x/100)
Solution:
Ex:
1. In a class o 22 students,
1.
there are 6 girls. What
percent of the class is girls?
2. There are 6 girls and 10
boys in the class. What
percent is girls?
To find the amount of change
- a discount is the amount of
decrease (the amount of
savings)
- a tip, sales tax, or commission is
the amount of increase (the
additional amount to be paid)
Ex:
1. The cost of dinner for Brad
and William was $38.00.
They want to leave a 15%
tip. What is the amount of
the tip they want to leave?
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©2009
6
x

22 100
600
3

 27 %
22
11
6
x

2. 16 100
600
1

 37 %
16
2
Change the % to decimaL by
moving the decimal point 2
decimal places to the Left,
making a decimal number. Then
multiply the original amount by
the decimal number to get the
amount of change.
1. 15% = 0.15
0.15 x $38.00 = $5.70
The tip amount is $5.70.
7.3A Percent Involving Word Problems
2. A sweatshirt that regularly
costs $36.00 is on sale at a
discount of 30%. What is
the amount of discount?
2. 30% = 0.30
0.30 x $36.00 = $10.80
The amount of discount is
$10.80.
#2 #1
x
To find percent of change

,
#1
100
(Percent of Increase or Percent of
Decrease), use a proportion or
solve for a percent using decimal For increases:
#1 is the beginning amount,
numbers.
#2 is the final amount,
#2 - #1 is the amount of change
(increase),
x/100 is the percent expressed
as a ratio (x per 100 or x/100)
3. World Toys buys bicycles
for $38 and sells them for
$95. What is the percent of
increase in the price?
95  38
x

38
100
57
x

38 100
3.
5700
 150% (increase)
38
#1 #2
x

,
#1
100
For decreases:
#1 is the beginning amount,
#2 is the final amount,
#1 - #2 is the amount of change
(decrease),
x/100 is the percent expressed
as a ratio (x per 100 or x/100)
TEKSING TOWARD TAKS
©2009
7.3A Percent Involving Word Problems
600  450
x
4. If the original price was

4.
600
100
$600 and the new price is
15,000
150
x
$450, what is the percent of

, 600 x  15,000 , x 
,
600
600 100
decrease?
x  25 , x = 25% (decrease)
150 1
  25% (decrease)
600 4
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©2009