1. Finding a Percent of a Number
LESSON 6-4
Check Skills You’ll Need
(For help, go to Lesson 1-9.)
1. Vocabulary Review The Distributive Property
combines the operation of ? with addition or subtraction.
Find each product using the Distributive Property and mental
math. See the example below for how to do this:
80 • 15 = 80(10 + 5) = 80(10) + 80(5) = = 1,200
2. 75 • 18 =
3. 78 • 0.9 =
4. 27 • 1.1 =
Check Skills You’ll Need
6-4

2. Finding a Percent of a Number
LESSON 6-4
Check Skills You’ll Need
(For help, go to Lesson 1-9.)
1. Vocabulary Review The Distributive Property
combines the operation of multiplication with addition or subtraction.
Find each product using the Distributive Property and mental
math. See the example below for how to do this:
80 • 15 = 80(10 + 5) = 80(10) + 80(5) = = 1,200
2. 75 • 18 = 75(10 + 8) = 75(10) + 75(8) = = 1,350
3. 78 • 0.9 = 78(1 – 0.1) = 78(1) – 78(0.1) = 78 – 7.8 = 70.2
4. 27 • 1.1 = 27( ) = 27(1) + 27(0.1) = = 29.7
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3. Finding a Percent of a Number
LESSON 6-4
Additional Examples
“of” means “multiply” so the expression is 15% • 40
Find each answer.
How else can you rewrite a percent?
a. 15% of 40
Method 1   Write 15% as a fraction and multiply.
Write the percent as a fraction in simplest form.
15% = = 15
100 3 20 3 20
• 40 = 6
Multiply.
Method 2   Write 15% as a decimal and multiply.
Write the percent as a decimal.
15% = 0.15
0.15 • 40 = 6
Multiply.
Which method do you prefer?
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4. Finding a Percent of a Number
LESSON 6-4
Additional Examples
(continued)
b. 80% of 460
Now do this on your own.
Method 1   Write 80% as a fraction and multiply.
Write the percent as a fraction in simplest form.
80% = = 80
100 4 5 4 5
• 460 = 368
Multiply.
Method 2   Write 80% as a decimal and multiply.
Write the percent as a decimal.
80% = 0.80
0.80 • 460 = 368
Multiply.
Quick Check
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5. Finding a Percent of a Number
LESSON 6-4
Additional Examples
Find each answer using mental math.
a. 49% of 300
Use the distributive property.
What you think
49% is 50% – 1%
50% of 300 is 0.5 • 300, or 150.
1% of 300 is 0.01 • 300, or 3.
So 150 – 3 = 147.
Why it works
0.49 • Write 49% as a decimal.
(0.50 – 0.01) • Substitute 0.50 – 0.01 for 0.49.
(0.50 • 300) – (0.01 • 300) Use the Distributive Property.
150 – Multiply.
Simplify.
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6. Finding a Percent of a Number
LESSON 6-4
Additional Examples
Find the answer using mental math.
b. 11% of 720
Now do this on your own.
What you think
11% is 10% + 1%
10% of 720 is 0.1 • 720, or 72.
1% of 720 is 0.01 • 720, or 7.2.
So = 79.2.
Why it works
0.11 • Write 11% as a decimal.
( ) • Substitute for 0.11.
(0.10 • 720) + (0.01 • 720) Use the Distributive Property.
Multiply.
Simplify.
Quick Check
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7. Finding a Percent of a Number
LESSON 6-4
Additional Examples
Estimate each answer.
a. 76% of 405
Write an expression.
76% • 405 3 4
• 400 = 300
Use compatible numbers such as and 400.
Check for Reasonableness  76% of 405 is 0.76 • 405, or 307.8,
which is close to the estimate 300. The answer is reasonable.
b. 12% of 5,575
Now do this on your own.
12% • 5,575
Write an expression.
• 5,600 = 560 1 10
Use compatible numbers such as and 5,600.
Check for Reasonableness  12% of 5,575 is 0.12 • 5,575, or 669,
which is close to the estimate 672. The answer is reasonable.
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8. Finding a Percent of a Number
LESSON 6-4
Additional Examples
(continued)
c. 48% of 925
Write an expression.
48% • 925 1 2
• 900 = 450
Use compatible numbers such as and 900.
Check for Reasonableness  48% of 925 is 0.48 • 925, or 444,
which is close to the estimate 450. The answer is reasonable.
Quick Check
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9. Finding a Percent of a Number
LESSON 6-4
Lesson Quiz
Find the percent of each number.
1. 40% of % of 45
3. 3.5% of % of 650 36 54
24.5
585
Homework:
Prepare for Chapter 5 Quiz
Practice 6-4 (handout)
Before you leave today, please leave your homework notebook on the ledge, open to the Ch 5 Corrections page.
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