Learn to estimate percents'

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Learn to estimate percents.
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The table shows common percents and their
fraction equivalents. You can use fractions to
estimate the percent of a number by choosing a
fraction that is close to a given percent.
10
20
25
50
1 4
1 5
1 3
2 3
1 2
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Additional Example 1 Using Fractions to Estimate
Percents
Use a fraction to estimate 27 of 63.
Think 27 is about 25 and 25 is
equivalent to .
1 4
63
27 of 63 ?
1 4
1 4
Change 63 to a compatible number.
60
?
? 15
Multiply.
27 of 63 is about 15.
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Try This Example 1
Use a fraction to estimate 48 of 91.
Think 48 is about 50 and 50 is
equivalent to .
1 2
91
48 of 91 ?
1 2
1 2
Change 91 to a compatible number.
90
?
Multiply.
? 45
48 of 91 is about 45.
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Additional Example 2 Consumer Math Application
Cary earns 9.88 per hour. He gets a bonus of 50
for each hour he works overtime. About how much
is he paid per hour for overtime?
First find the bonus for each hour of overtime.
1 2
1 2
9.88
50 of 9.88
Think 50 is equivalent to .
1 2
Change 9.88 to a compatible number.
10
?
? 5
Multiply.
The bonus is approximately 5. Since 10 5
15, he earns about 15 for each hour he works
overtime.
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Insert Lesson Title Here
Try This Example 2
Billy has a job assembling office furniture. He
is paid 9.20 for each unit completed. If he
completes more than 10 units a week he is paid an
additional 25 per unit. How much is he paid for
each unit above 10.
First find the additional amount earned for each
unit above 10.
1 4
1 4
25 of 9.20
9.20
Think 25 is equivalent to .
1 4
Change 9.20 to a compatible number.
9
?
? 2.25
Multiply.
The bonus for each extra unit is approximately
2.25. Since 9 2.25 11.25, he earns about
11.25 for each extra unit.
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Another way to estimate percents is to find 1 or
10 of a number. You can do this by moving the
decimal point in the number.
.
1 of 45
.
45
10 of 45
45
.
.
To find 1 of a number, move the decimal point
two places to the left.
To find 10 of a number, move the decimal point
one place to the left.
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Additional Example 3A Estimating with Simple
Percents
Use 1 or 10 to estimate the percent of each
number.
A. 4 of 18
18 is about 20, so find 4 of 20.
1 of 20 20.
.
4 of 20 4 0.2 0.8
4 equals 4 1.
4 of 18 is about 0.8.
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Additional Example 3B Estimating with Simple
Percents
Use 1 or 10 to estimate the percent of each
number.
B. 29 of 80
29 is about 30, so find 30 of 80.
10 of 80 80.
.
30 of 80 3 8.0 24.0
30 equals 3 10.
29 of 80 is about 24.
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Try This Example 3A
Use 1 or 10 to estimate the percent of each
number.
A. 5 of 14
14 is about 15, so find 5 of 15.
1 of 15 15.
.
5 of 15 5 0.15 0.75
5 equals 5 1.
5 of 14 is about 0.75.
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Try This Example 3B
Use 1 or 10 to estimate the percent of each
number.
B. 21 of 60
21 is about 20, so find 20 of 60.
10 of 60 60.
.
20 of 60 2 6.0 12.0
20 equals 2 10.
21 of 60 is about 12.
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Additional Example 4 Consumer Math Application
Tim spent 58 on dinner for his family. About how
much money should he leave for a 15 tip?
Since 58 is about 60, find 15 of 60.
15 10 5
Think 15 is 10 5.
10 of 60 6
5 of 60 6 2 3
6 3 9
Add the 10 and 5 estimates.
Tim should leave about 9 for a 15 tip.
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Try This Example 4
Amanda spent 12 on a hair cut. About how much
money should she leave for a 15 tip.
Since 12 is about 10, find 15 of 10.
15 10 5
Think 15 is 10 5.
10 of 10 1
5 of 10 1 2 0.50
1 0.50 1.50
Add the 10 and 5 estimates.
Amanda should leave about 1.50 for a 15 tip.
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Insert Lesson Title Here
Lesson Quiz
Use a fraction to estimate the percent of each
number. 1. 48 of 72 2. 26 of 80 Use 1 or
10 to estimate the percent of each number. 3. 4
of 220 4. 19 of 75 5. Mr. and Mrs. Dargen spend
46.25 on a meal. About how much should they
leave for a 15 tip?
Possible answers
36
20
Possible answers
8.8
15
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