Learn to find the percent of a number'

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Learn to find the percent of a number.
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The human body is made up mostly of water. In
fact, about 67 of a persons total (100) body
weight is water. If Cameron weighs 90 pounds,
about how much of his weight is water?
A percent is a part of 100. Since you want to
know the part of Camerons body that is water,
you can set up and solve a proportion to find the
answer.
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Additional Example 1A Using Proportions to Find
Percents of Numbers
Find the percent of each number.
A. 30 of 50
30 100
n 50

Write a proportion.
30 50 100 n
Set the cross products equal.
1,500 100n
Multiply.
1,500
100n
Divide each side by 100 to isolate the variable.

100
100
15 n
30 of 50 is 15.
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Additional Example 1B Using Proportions to Find
Percents of Numbers
Find the percent of each number.
B. 200 of 24
200 100
n 24

Write a proportion.
200 24 100 n
Set the cross products equal.
4,800 100n
Multiply.
4,800
100n
Divide each side by 100 to isolate the variable.

100
100
48 n
200 of 24 is 48.
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Try This Example 1A
Find the percent of each number.
A. 40 of 40
40 100
n 40

Write a proportion.
40 40 100 n
Set the cross products equal.
1,600 100n
Multiply.
1,600
100n
Divide each side by 100 to isolate the variable.

100
100
16 n
40 of 40 is 16.
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Try This Example 1B
Find the percent of each number.
B. 150 of 64
150 100
n 64

Write a proportion.
150 64 100 n
Set the cross products equal.
9,600 100n
Multiply.
9,600
100n
Divide each side by 100 to isolate the variable.

100
100
96 n
150 of 64 is 96.
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In addition to using proportions, you can find
the percent of a number by using decimal
equivalents.
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Additional Example 2A Using Decimal Equivalents
to Find Percents of Numbers
Find the percent of the number. Estimate to check
whether your answer is reasonable.
A. 9 of 80
Write the percent as a decimal and multiply.
9 of 80 0.09 80
7.2
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Additional Example 2B Using Decimal Equivalents
to Find Percents of Numbers
Find the percent of the number. Estimate to check
whether your answer is reasonable.
B. 3 of 12
3 of 12 0.03 12
Write the percent as a decimal and multiply.
0.36
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Insert Lesson Title Here
Try This Example 2A
Find the percent of the number. Estimate to check
whether your answer is reasonable.
A. 21 of 50
21 of 50 0.21 50
Write the percent as a decimal and multiply.
10.5
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Try This Example 2B
Find the percent of the number. Estimate to check
whether your answer is reasonable.
B. 6 of 18
6 of 18 0.06 18
Write the percent as a decimal and multiply.
1.08
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Additional Example 3 Geography Application
The estimated world population in 2001 was 6,157
million. About 40 of the people were 19 or
younger. What was the approximate number of
people 19 or younger, to the nearest million?
Find 40 of 6,157 million
0.40 6,157
Write the percent as a decimal.
Multiply.
2,462.8
The number of people 19 or younger was about
2,463 million.
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Try This Example 3
The estimated world population in 2001 was 6,157
million. About 60 of the people were above 19
years of age. What was the approximate number of
people 19 or older, to the nearest million?
Find 60 of 6,157 million.
0.60 6,157
Write the percent as a decimal.
3,694.2
Multiply.
The number of people 19 or older was about 3,694
million.
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Insert Lesson Title Here
Lesson Quiz
Find the percent of each number. 1. 25 of 8
2. 40 of 110 3. 150 of 96 4. 0.3 of 120 5.
Whitmer Middle School has 850 students. If 42
of the students bought lunch on Monday, how many
student bought lunch on Monday?
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44
144
0.36
357