6.5
Percents
Per
Cent from Latin – per centum - per hundred
4%
Interest - $4 per $100 
Definition
of percent 
Demonstrate
some Shading with Transparency
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100 Grid |
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100 Grid |
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As a Group
Activity in Class - Chapter 6 - Activity 10
and some of 11
Convert Fraction or Decimal to
percent
A)
Method I. Multiply by 1 = 100%
i.e. Move decimal 2 places to the right and add %
sign.
0.07 
1.4 0.00022
2 
B)
Method II. Convert using proportions 
Convert
percent to Decimal
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15% |
9.2% |
0.6% |
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450% |
400% |
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IMPORTANT
versus 
Look at 100 grid!!
1 versus 1%
2.3 versus 2.3 %
Three
Traditional Forms of Percent Problems
(
)
1. Finding a percent of a number. (Find 
)
2. Finding what
percent one number is of another. (Find
)
3. Finding a
number when a percent of that number is known.
(Find 
)
Recall:
"of" means times
Examples
of each type:
1.
Find 15% of 70.
2.
What % of 80 is 70?
3.
80% of what number is 60?
Mental Math with Percents
Common fraction equivalents - table pg. 414
Percent
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Fraction
Equivalent |
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Applications
Great examples in text - each is done by at least 2 methods
Gail made
$16,000 last year and received a 6% raise. How much does she make now?
A used car
originally cost $1700. One year later, it was worth $1400. What is
the percentage of depreciation?
If a ¼ c.
serving of Crunchies breakfast food has 0.5% of the minimum daily requirement
of vitamin C, how many cups would you have to eat to obtain the minimum daily
requirement of vitamin C?
Bill got 52
correct answers on an 80-question test. What percent of the questions did
he answer incorrectly?
a.
How can an estimate of 10% of a number help you estimate 35% of the number?
b.
Mentally compute 35% of $8.00
What is 40%
of 50% of a number?
An
advertisement reads that if you buy ten items you get 20% off your total
purchase price. You need 8 items that cost $9.50 each.
a. How much would 8 items cost? 10 items?
b. Is it more economical to buy 8 items of 10 items?
John paid
$330 for a new mountain bicycle to sell in his shop. He wants to price it
so that he can offer a 10% discount and still make 20% of the price he paid for
it. At what price should the bike be marked?
READ on OWN
Mental math with % - page 414-415
Estimation w/Percent - pg. 415-416