Math 103
Chapter 10 QuizSolutions
April 1,
2011
Problems 14 are 5 points each.
1. In September, the Goodprices store was selling an astronomy book for
20% over cost (20% increase). In October the book went on sale for 20%
off.
In November the book price was reduced by 8.5%.
a. After the increase and decreases, was there a percentage profit or loss
to the store?
20% increase means multiply by 1+.20=1.20
20% decrease means multiply by 1.20=0.80
8.5% decrease means multiply by 1.085=.915
1.20*0.80*0.915=0.878
Since 0.878 is less than 1, there is a percentage loss.
It is 10.878=0.122 or a 12.2% decrease
Note that 1.122=.878
That is, if the original price is P, then the new price is P
0.122P=0.878P,
A 12.2% decrease in the price.
b. What is the percentage profit or loss?
12.2% loss
c. If the original price of the book was $150, what is the final price of the
book?
0.878*$150=$131.70
2. Formula for simple interest is F=P(1+rt).
You deposit $5400 in the bank where it earns
simple
interest for 8 years.
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At the end of that time, you have $8316. Determine the APR for your
deposit
F=P(1+rt)
F=8316
P=5400
t=8
8316=5400(1+8r)
8316/5400=1+8r
1.54=1+8r
.54=8r
R=.54/8=.0675 =6.75%
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 Spring '07
 Berkowitz
 Math, Annual Percentage Rate, Future Value, Bank B

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