GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 22 Sep 2018, 15:50

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

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

Author Message
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 49303
Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ?  [#permalink]

Show Tags

25 Jun 2018, 05:59
00:00

Difficulty:

5% (low)

Question Stats:

84% (00:49) correct 16% (01:09) wrong based on 238 sessions

HideShow timer Statistics

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

NEW question from GMAT® Official Guide 2019

(PS10470)

_________________
e-GMAT Representative
Joined: 04 Jan 2015
Posts: 2007
Re: Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ?  [#permalink]

Show Tags

25 Jun 2018, 06:09
1

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.

_________________

Number Properties | Algebra |Quant Workshop

Success Stories
Guillermo's Success Story | Carrie's Success Story

Ace GMAT quant
Articles and Question to reach Q51 | Question of the week

Number Properties – Even Odd | LCM GCD | Statistics-1 | Statistics-2
Word Problems – Percentage 1 | Percentage 2 | Time and Work 1 | Time and Work 2 | Time, Speed and Distance 1 | Time, Speed and Distance 2
Advanced Topics- Permutation and Combination 1 | Permutation and Combination 2 | Permutation and Combination 3 | Probability
Geometry- Triangles 1 | Triangles 2 | Triangles 3 | Common Mistakes in Geometry
Algebra- Wavy line | Inequalities

Practice Questions
Number Properties 1 | Number Properties 2 | Algebra 1 | Geometry | Prime Numbers | Absolute value equations | Sets

| '4 out of Top 5' Instructors on gmatclub | 70 point improvement guarantee | www.e-gmat.com

CEO
Joined: 12 Sep 2015
Posts: 2878
Re: Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ?  [#permalink]

Show Tags

25 Jun 2018, 06:09
Top Contributor
Bunuel wrote:
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

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

$$≈ \sqrt{4(100)}$$

$$≈ \sqrt{400}$$

$$≈ 20$$

RELATED VIDEO FROM OUR COURSE

_________________

Brent Hanneson – GMATPrepNow.com

Director
Joined: 31 Oct 2013
Posts: 577
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ?  [#permalink]

Show Tags

28 Jun 2018, 03:59
Bunuel wrote:
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

NEW question from GMAT® Official Guide 2019

(PS10470)

4.2 ~ 4
1590~1600
15.7~16

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

Thus the best answer is A.
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 3515
Location: United States (CA)
Re: Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ?  [#permalink]

Show Tags

28 Jun 2018, 18:04
Bunuel wrote:
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

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

√[(42)(1,590)/157]

Approximating, we have:

√[(40)(1,600)/160]

√[(40)(10)] = √400 = 20

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: Which of the following is closest to (4.2(1,590)/15.7)^(1/2) ? &nbs [#permalink] 28 Jun 2018, 18:04
Display posts from previous: Sort by

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

Events & Promotions

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.