Checklist
Notes
The intent of this unit:
Describe change with percents.
Compare values with percents.
Inspect ’of’ versus ’more than’ worded statements.
Describe percentage points differences.
Solve percent problems (tax, tip).
Find common fallacies with percents.
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Assignment
Notes
Assignment:
1. p 140 - 141 Quick Quiz
2. p 141 Does It Make Sense? 7 - 16
3. p 142 - 143 Excercises 45, 47, 51, 53, 55, 57, 59, 63,
67, 71, 75, 77, 83, 85, 87, 89
What is the difference between the key words ’or’ and
’more than?’
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Key Words
Notes
Absolute Change Describes actual increase /
decrease from a reference value to a new value.
Relative Change Describes as a fraction the size of
the absolute change to the reference value.
Percentage Change Conversion of the relative
change by multiplying with 100%.
Absolute Difference The actual difference be5tween
the compared value and the reference value.
Relative Differenc Describes the size of the absolute
difference as a fraction of the reference value.
Percentage Difference Conversion of the relative
difference by multiplying with 100%.
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Review of Percents
Notes
Conversions:
Percent into Fraction - Replace % with ÷ by 100.
Ex: 12% = 12/100 = 3/25
Percent into Decimal (LID) - Drop % and move
decimal two places left.
Ex: 12% = 0.12
Decimal into Percent (RIP) - Move decimal two place
right and add the %.
Ex: 0.48 = 48%
Fraction into Percent - Convert to decimal, then use
RIP.
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Examples
Notes
(Example 3 - p 131) - World population was 2.6 billion in
1950 and 6.0 billion in 2000. Describe the change using
an absolute difference, relative difference, and percentage
difference.
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Examples
Notes
(Example 4 - p 131) - You bought a computer three years
ago for $1000. Today, it is worth only $300. Describe the
change using an absolute difference, relative difference,
and percentage difference.
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Examples
Notes
Suppose you want to compare the price of a $50,000
Mercedes to the price of a $40,000 Lexus. Do the
comparision and switch which price is the reference value.
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Examples
Notes
(Example 6 - p 134) Carol earns 50% more than William.
How many times larger is her income than his? (What
percent is Carol’s income of William’s income?)
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Examples
Notes
(Example 8 - p 135) The percentage of adults who report
reading a daily newspaper fell from about 78% in 1980 to
49% in 2009. Describe this change in newspaper
readership. (Use absolute change and relative change.)
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Examples
Notes
(Example 10, 11 p 136 - 137) a. You buy a shirt with
pre-tax price of $17. The local sales tax rate is 5%. What
is your final cost, with tax?
b. Your receipt shows that you paid $19.62 for a Blu-ray
disc, tax included. The local sales tax rate is 7%. What
was the pre-tax price of the disc?
Consider the report: ”The rate of smoking for eighth
grades is up 44 percent, to 10.4 percent.” What was the
previous smoking rate for eighth-graders?
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Notes
Notes