Transcript Find the percent of the number. Check whether your answer is

6-4 Percent of a Number
Learn to find the percent of a number.
Course 2
6-4 Percent of a Number
The human body is made up mostly of water. In fact, about
67% of a person’s total (100%) body weight is water. If
Cameron weighs 90 pounds, about how much of his weight is
water?
Recall that a percent is a part of 100. Since you want to know
the part of Cameron’s body that is water, you can set up and
solve a proportion to find the answer.
Part
Whole
Course 2
n
67
=
100 90
Part
Whole
6-4 Percent of a Number
Additional Example 1A: Using Proportions to Find
Percents of Numbers
Find the percent of each number.
30% of 50
30 = n
100
50
30 · 50 = 100 · n
Set the cross products equal.
1,500 = 100n
Multiply.
1,500 = 100n
100
100
15 = n
Divide each side by 100 to isolate
the variable.
30% of 50 is 15.
Course 2
Write a proportion.
6-4 Percent of a Number
Check It Out: Example 1A
Find the percent of each number.
40% of 40
40 = n
100
40
40 · 40 = 100 · n
Set the cross products equal.
1,600 = 100n
Multiply.
1,600 = 100n
100
100
16 = n
Divide each side by 100 to isolate
the variable.
40% of 40 is 16.
Course 2
Write a proportion.
6-4 Percent of a Number
Check It Out: Example 1B
Find the percent of each number.
150% of 64
150 = n
100
64
150 · 64 = 100 · n
9,600 = 100n
9,600
100
= 100n
100
96 = n
150% of 64 is 96.
Course 2
Write a proportion.
Set the cross products equal.
Multiply.
Divide each side by 100 to isolate
the variable.
6-4 Percent of a Number
In addition to using proportions, you can find the
percent of a number by using decimal equivalents.
Course 2
6-4 Percent of a Number
Additional Example 2A: Using Decimal Equivalents
to Find Percents of Numbers
Find the percent of the number. Check whether your answer is
reasonable.
9% of 80
Write the percent as a decimal
and multiply.
9% of 80 = 0.09 · 80
= 7.2
9%
Model
Since 10% of 80 = 8, a reasonable answer for 9% of 80 is
7.2.
40%
20%
0
20
0
7.2
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60%
40
80%
60
100%
80
6-4 Percent of a Number
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.
3% of 12
3% of 12 = 0.03 · 12
= 0.36
Write the percent as a decimal
and multiply.
Estimate
5% · 12 = 0.6, so 3% of 12 is a little less than 0.6. Thus 0.36 is
a reasonable answer.
Course 2