It is currently 20 Nov 2018, 03:37
My Tests

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

GRE Math Challenge #69-If the radius of a circular region

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 07 Jun 2014
Posts: 4720
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 91

Kudos [?]: 1622 [0], given: 385

CAT Tests
GRE Math Challenge #69-If the radius of a circular region [#permalink] New post 03 May 2015, 01:23
Expert's post
00:00

Question Stats:

100% (00:07) correct 0% (00:00) wrong based on 2 sessions
If the radius of a circular region were decreased by 20 percent, the area of the circular region would decrease by what percent?

A. 16%
B. 20%
C. 36%
D. 40%
E. 44%
[Reveal] Spoiler: OA

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Director
Director
Joined: 20 Apr 2016
Posts: 743
Followers: 6

Kudos [?]: 500 [0], given: 86

CAT Tests
Re: GRE Math Challenge #69-If the radius of a circular region [#permalink] New post 12 Dec 2017, 11:24
sandy wrote:
If the radius of a circular region were decreased by 20 percent, the area of the circular region would decrease by what percent?

A. 16%
B. 20%
C. 36%
D. 40%
E. 44%



Let us take the radius as = 10
Therefore the area of the circular region = \(pi * r^2\)

=\(pi *10^2\)
=100pi

Now the radius is decreased by 20 percent

i.e 10-(10 * 0.2) = 8, which is the new radius

Therefore area of the circular region with the new radius = \(pi * 8^2\)
=64pi

Therefore the area of the circular region decreased = \(\frac{(New - old)}{old}\) = \(\frac{(64pi - 100pi)}{100pi}\)= \(-36%\) (The value is negative because the percentage is decreased)
_________________

If you found this post useful, please let me know by pressing the Kudos Button

Re: GRE Math Challenge #69-If the radius of a circular region   [#permalink] 12 Dec 2017, 11:24
Display posts from previous: Sort by

GRE Math Challenge #69-If the radius of a circular region

  Question banks Downloads My Bookmarks Reviews Important topics  


GRE Prep Club Forum Home| About| Terms and Conditions and Privacy Policy| GRE Prep Club Rules| Contact

Powered by phpBB © phpBB Group

Kindly note that the GRE® test is a registered trademark of the Educational Testing Service®, and this site has neither been reviewed nor endorsed by ETS®.