Pre-Algebra Chapter 6 - Ramsey School District

c. Estimate 1 % of 598.
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1 3 % 1 1%. 598 is almost 600.
3
1% of 600 is 6.
So, 1 3 % of 598 is about 1 6 or 2.
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d. Estimate 118% of 56.
118% means about 120 for every 100 or about 12 for every 10.
56 has about 6 tens.
12 6 72
So, 118% of 56 is about 72.
Estimating percents is a useful skill in real-life situations.
Study Tip
Finding Percents
To find 10% of a number,
move the decimal point
one place to the left.
Example 3
Use Estimation to Solve a Problem
MONEY Amelia takes a taxi from the airport to a hotel. The fare is $31.50.
Suppose she wants to tip the driver 15%. What would be a reasonable
amount of tip for the driver?
$31.50 is about $32.
15% 10% 5%
10% of $32 is $3.20. Move the decimal point 1 place to the left.
5% of $32 is $1.60. 5% is one half of 10%.
So, 15% is about 3.20 1.60 or $4.80.
A reasonable amount for the tip would be $5.
Concept Check
Guided Practice
GUIDED PRACTICE KEY
1. Explain how to estimate 18% of 216 using the fraction method.
2. Estimate the percent of the figure
that is shaded.
3. OPEN ENDED Tell which method
of estimating a percent you prefer.
Explain your decision.
Find the percent of each number mentally.
4. 75% of 64 5. 25% of 52
6. 33 1 % of 27 7. 90% of 80
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Application
www.pre-alg.com/extra_examples
Estimate. Explain which method you used to estimate.
8. 20% of 61 9. 34% of 24
10. 1 % of 396 11. 152% of 14
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12. MONEY Lu Chan wants to leave a tip of 20% on a dinner check of
$52.48. About how much should he leave?
Lesson 6-6 Finding Percents Mentally 295