Solved Examples and Worksheet for Estimation-Percentages

Q1A man buys a Compact Stereo System for $135. The sales tax is 6%. Estimate the sales tax and the final cost.

A. $143.1, $8.1
B. $8.1, $143.1
C. $8.1, $126.9
D. $6, $141

Solutions
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Step: 1
The sales tax is 6% of 135.
Step: 2
6% = 6100 = 0.06
  [Divide 6 by 100 to convert it into decimal.]
Step: 3
Sales tax = 0.06 x 135 = $8.1
  [Multiply the decimal by the cost of Compact Stereo System.]
Step: 4
Final cost = cost + sales tax = 135 + 8.1 = $143.1
  [Add.]
Step: 5
The sales tax on the Compact Stereo System is $8.1 and the final cost is $143.1.
Correct Answer is :   $8.1, $143.1
Q2Estimate 40% of 125.
A. 96
B. 48
C. 144
D. None of the above

Solutions
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Step: 1
40% of 125
  [Expression to be evaluated.]
Step: 2
= 820 of 125
  [Rewrite 40% with an equal fraction 40100 or 820.]
Step: 3
= 820 × 120
  [Replace 125 with 120, which is compatible with the fraction.]
Step: 4
= 81 × 6
  [Cancel 120 with 20 .]
Step: 5
= 48
  [Simplify.]
Step: 6
40% of 125 is 48.
Correct Answer is :   48
Q3Estimate 48% of 70.

A. 33
B. 37
C. 39
D. 35

Solutions
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Step: 1
48% of 70
  [Original expression.]
Step: 2
A fraction with denominator 2 is compatible with 70, as 70 is a multiple of 2.
Step: 3
≈ 12 x 70
  [Rewrite 48% as 50% or 50100 or 12.]
Step: 4
= 35
  [Cancel 70 with 2 and simplify.]
Correct Answer is :   35
Q4Estimate 15.4% of 18.

A. 2.5
B. 3.5
C. 4
D. 3

Solutions
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Step: 1
15.4% of 18
  [Original expression.]
Step: 2
≈ 320of 18
  [Rewrite 15.4% as 15% or 15100 or 320.]
Step: 3
≈ 320 x 20
  [Replace 18 with 20 as it is compatible with the fraction.]
Step: 4
= 32 x 2
  [Cancel 20 and 20 with 10.]
Step: 5
= 1.5 x 2
  [Divide 3 by 2.]
Step: 6
= 3
  [Multiply.]
Correct Answer is :   3
Q5Estimate 25% of 138.

A. 30
B. 40
C. 25
D. 35

Solutions
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Step: 1
25% of 138
  [Original expression.]
Step: 2
= 14 of 138
  [Write 25% as 25100 or 14.]
Step: 3
≈ 14 x 140
  [Since 140 is a multiple of 4, rewrite 138 as 140.]
Step: 4
= 35
  [Cancel 140 with 25 and simplify.]
Correct Answer is :   35
Q6Estimate 32.4% of 900.

A. 265
B. 275
C. 270
D. 260

Solutions
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Step: 1
32.4% of 900
  [Original expression.]
Step: 2
900 is a multiple of 10. So, a fraction with denominator 10 is compatible with 900.
Step: 3
≈ 310 x 900
  [Rewrite 32.4 as 30% or 30100 or 310.]
Step: 4
= 270
  [Cancel 900 with 10 and simplify.]
Correct Answer is :   270
Q7John went out for a dinner. The bill was $38.93. Which of the following is a good estimate of a 20% tip on the bill?
A. $20.00
B. $3.50
C. $8.00
D. $15.00

Solutions
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Step: 1
20% of 38.93
  [Expression to be evaluated.]
Step: 2
= 20100 of 38.93
  [Rewrite 20% with an equal fraction 20100.]
Step: 3
= 20100of 40
  [Replace 38.93 with 40, which is compatible with the fraction.]
Step: 4
= 15× 40
Step: 5
= 8
  [Simplify.]
Step: 6
So, a good estimate of a 20% tip on the bill $38.93 is $8.
Correct Answer is :   $8.00
Q8Express 42 out of 100 as a percentage.

A. 42
B. 42%
C. 0.42
D. 32100

Solutions
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Step: 1
42 out of 100 is 42100 .
Step: 2
42 × 1100 = 42%
Step: 3
So, 42100 = 42%
Correct Answer is :   42%

HighSchool Math