1. Chapter 6
Percent
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6.1 Basics of Percent
Objectives
1. Learn the meaning of percent.
2. Write percents as decimals.
3. Write decimals as percents.
4. Understand 100%, 200%, and 300%.
5. Use 50%, 10%, and 1%.
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The figure has one hundred squares of equal size. Eleven of the square are shaded. The shaded portion is or 0.11 of the total figure. The shaded portion is also 11% of the total or “eleven parts out of 100 parts.” Read 11% as “eleven percent.”
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Parallel
Example 1
Understanding Percent
If 52 out of 100 chickens are hens, then 52 per 100 or , or 52% of the chickens are hens.
b. If a person pays a tax of $9 on every $100 of purchases, then the tax rate is $9 per $100. The ratio is and the percent of tax is 9%.
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Parallel
Example 2
Writing Percents as Decimals
Write each percent as a decimal.
32%
p% = p ÷ 100
32% = 32 ÷ 100 = 0.32
78%
78% = 78 ÷ 100 = 0.78
93.4%
93.4% = 93.4 ÷ 100 = 0.934
200%
200% = 200 ÷ 100 = 2.00
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Parallel
Example 3
Writing Percents as Decimals by Moving the Decimal Point
Write each percent as a decimal by moving the decimal point two places to the left.
23%
23.%
0.23
23% = 0.23
180%
180.% =
Decimal point starts at far right side
Percent sign is dropped (Step 1)
Decimal point is moved two places to the left. (Step 2)
180.%
= 1.80 or 1.8
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Parallel
Example 3
Writing Percents as Decimals by Moving the Decimal Point
Write each percent as a decimal by moving the decimal point two places to the left.
c %
is attached so the decimal point can be moved two places to the left.
0.7%
0.7% =
0.007
Two zeros are attached so the decimal point can be moved two places to the left.
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Parallel
Example 4
Writing Decimals as Percents by Moving the Decimal Point
Write each decimal as a percent by moving the decimal point two places to the right.
0.26
Decimal point is moved two places to the right.
0.26 = 26% b
Percent sign is attached and decimal point is not written with whole number percents.
= 37.6%
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Parallel
Example 4
Writing Decimals as Percents by Moving the Decimal Point
Write each decimal as a percent by moving the decimal point two places to the right.
1.83
d. 3.4
3.4 = 340% 5
5. = 5.00
so 5 = 500%
= 183%
= 3.40
0 is attached so the decimal point can be moved two places to the right.
Attach % sign.
Two zeros are attached so the decimal point can be moved two places to the right.
Attach % sign.
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When working with percents, it is helpful to have several reference points. 100%, 200% and 300% are three such reference points. 100% means 100 parts out of 100 parts. That’s all of the parts. If 100% of the 18 people attending last week’s meeting attended this week’s meeting, then 18 people (all of them) attended this week.
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Parallel
Example 5
Finding 100%, 200%, and 300% of a Number
Fill in the blanks.
100% of 24 people is _____.
100% is all of the people.
100% of 24 people is 24 people.
200% of $25 is _____.
200% is twice (2 times) as much money.
200% of $25 is 2  $25 = $50.
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Parallel
Example 5
Finding 100%, 200%, and 300% of a Number
Fill in the blanks. c. 300% of 12 animals is _____. 300% is 3 times as many animals. 300% of 12 animals is 3  12 = 36 animals.
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50% means 50 parts out of 100 parts, which is half of the parts. So, 50% of $24 is $12 (half of the money). 10% means 10 parts out of 100. To find 10% of a number we move the decimal point one place to the left. To find 1% of a number, we move the decimal point two places to the left.
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Parallel
Example 6
Finding 50%, 10%, and 1% of a Number
Fill in the blanks.
50% of 36 hours is _____.
50% is half of the hours.
50% of 36 is 18 hours.
10% of 320 pages is _____.
Move the decimal point one place to the left.
10% of 320 is 32 pages.
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Parallel
Example 6
Finding 50%, 10%, and 1% of a Number
Fill in the blanks. c. 1% of $780 is _____. Move the decimal point two places to the left. 1% of $780 is $7.80.
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