1. Finding a Percent of a Number
COURSE 2 LESSON 6-4
Finding a Percent of a Number
Find each answer using mental math.
a. 49% of 300
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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2. Finding a Percent of a Number
COURSE 2 LESSON 6-4
Finding a Percent of a Number
(continued)
b. 11% of 7220
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.
6-4

3. Finding a Percent of a Number
COURSE 2 LESSON 6-4
Finding a Percent of a Number
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
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.
6-4

4. Finding a Percent of a Number
COURSE 2 LESSON 6-4
Finding a Percent of a Number
(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.
6-4

5. Finding a Percent of a Number
COURSE 2 LESSON 6-4
Finding a Percent of a Number
Find the percent of each number.
1. 40% of % of 45
3. 3.5% of % of 650 36 54
24.5
585
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