Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ?

Question

Which of the following is closest to  \sqrt{\frac{4.2(1,590)}{15.7}} ?

A. 20
B. 40
C. 60
D. 80
E. 100

(PS10470)

EgmatQuantExpert · Accepted Answer

Solution

To find:  
• The value closest to the expression  \sqrt{\frac{4.2(1,590)}{15.7}}

Approach and Working:  
As we are trying to find out the closest value, we can approximate the given terms as follows:
 • 4.2 ~ 4
• 1590 ~ 1600
• 15.7 ~ 16

Therefore, we can rewrite the expression as  \sqrt{\frac{4(1,600)}{16}}  =  \sqrt{4 * 100}  = 20

Hence, the correct answer is option A.

Answer: A

BrentGMATPrepNow · Answer

ALWAYS check the answer choices before solving the question!   
When we do so, we see that the answer choices are VERY spread apart, which means we can save a ton of time by being super aggressive with our approximations (aka rounding)

So, we get:  \sqrt{\frac{4.2(1,590)}{15.7}} ≈ \sqrt{\frac{4(1,600)}{16}}

≈ \sqrt{4(100)}

≈ \sqrt{400}

≈ 20

Answer: A

RELATED VIDEO FROM OUR COURSE
 https://www.youtube.com/watch?v=8GqcJGUVIk4

KSBGC · Answer

4.2 ~ 4
1590~1600
15.7~16

\frac{4*1600}{16} 
= \sqrt{(400)} 
= 20

Thus the best answer is A.

ScottTargetTestPrep · Answer

First we can multiply the fraction by 10/10 and we have:

√

Approximating, we have:

√

√  = √400 = 20

Answer: A

dimri10 · Answer

root of 4, 2
root of 1600, 40
root of 16, 4
2*40/4 is 20

MHIKER · Answer

\sqrt{\frac{4.2(1,590)}{15.7}}

= \sqrt{\frac{4*1,600}{16}}

=\sqrt{4*100}

=2*10

=20

GMATinsight · Answer

Answer: Option A

Video solution by  GMATinsight

https://www.youtube.com/watch?v=b5irb5fLMgU

bumpbot · Answer

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Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ?

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GMAT Problem Solving (PS) Questions

Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ?

Prep Toolkit

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More than Quant/Verbal Abilities: Speed vs. Accuracy

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From 555 to 765: 210-point Improvement

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My Rewards