unit 3 - prealgebra lesson plans · unit 3 chapter 7-3 fractions, decimals, and percents....
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UNIT 3Chapter 7-3
Fractions, Decimals, and Percents
Vocabulary
■ A percent is a ratio that compares a
number to 100. The meaning of
75% is shown at the right. In the
figure, 75 out of 100 squares are
shaded.
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Percents as Fractions
■ To write a percent as a fraction, express the ratio as a fraction with a denominator of 100.
Then simplify, if possible. Note that a percent can be greater than a 100% or less than 1%.
■ Express each percent as a fraction in simplest form
■ Example 1: Example 2: Example 3: Multiply by 10
10
45% = 45
100120% =
120
100.5% =
.5
100to eliminate decimal
= 9
25=
6
5= 1
1
5=
5
1000=
1
200
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Write Fraction as Percent
■ To write a fraction as a percent, write an equivalent fraction with a denominator of
100.
■ Example 1: Example 2:
4
5
9
4
= 4
5=
80
100=
9
4=
225
100
= 80% =225%
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Let’s Practice!
■ Write each percent as a fraction and a decimal
Ex 1) 20% Ex 2) 85% Ex 3)110%
■ Write each fraction as a percent
Ex 4) 1
10Ex 5)
2
5
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Let’s Check Our Answers!
■ Write each percent as a fraction and a decimal
Ex 1) 20% Ex 2) 85% Ex 3)110%
20
100=
1
5, .2
85
100=
17
20, .85
110
100=
11
10, 1.1
■ Write each fraction as a percent
Ex 4) 1
10Ex 5)
2
5
= 10% = 40%
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Write Percents and Decimals
■ To write a percent as a decimal, divide by 100 (or move the decimal
two places to the left) and remove the percent symbol
■ To write a decimal as a percent, multiply by 100 (or move the decimal
two places to the right) and add the percent symbol
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Write Percents as Decimal
■ Express each percent as a decimal (Remember, divide by 100 or move the decimal
two places to the left)
Ex 1) 28% ----divide by 100 and remove the %
28% = 28% = .28
Ex 2) 8% Ex 3) 375%
8% = 8% = .08 375% = 3 7 5% = 3.75%
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Write Decimals as Percents
■ Express each decimal as a percent --- (Remember, multiply by 100 and add the % or
move the decimal two places to the right)
Ex 1) .35 Ex 2) .007 Ex 3) 1.35
. 35 = .35 = 35% .007 = .0 0 7 = .7% 1.35 = 1. 3 5 = 135%
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Fractions as a Percent
■ When expressing a fraction as a percent, express the fraction as a decimal then
express the decimal as a percent
■ Example 1) 5
8Ex 2)
5
6
= .625 = 62.5% = .833333
= 83.3%
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Remember…
■ Fractions, decimals, and percents are all different names that represent the same
number
1
2
.5 50%
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Let’s Practice
■ Write the percent as a decimal
Ex 1) 50% Ex 2) 35% Ex 3) 2%
■ Write the decimal as a percent
Ex 4) .75 Ex5) .05 Ex 6) 1.15
■ Write the fraction as a percent
Ex 7) 5
8Ex 8)
1
3
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Let’s Check Our Answers!
■ Write the percent as a decimal
Ex 1) 50% Ex 2) 35% Ex 3) 2%
=.50 .35 = . 02
■ Write the decimal as a percent
Ex 4) .75 Ex5) .05 Ex 6) 1.15
= 75% = 5% = 115%
■ Write the fraction as a percent. Round to the nearest tenth if needed
Ex 7) 5
8Ex 8)
1
3
= 62.5% = 33.3%
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