It is currently 09 Dec 2018, 22:02
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.

If the diameter (d ) of a circle is an integer and 6 cm ≤ d

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Moderator
Moderator
User avatar
Joined: 18 Apr 2015
Posts: 5122
Followers: 76

Kudos [?]: 1022 [0], given: 4624

CAT Tests
If the diameter (d ) of a circle is an integer and 6 cm ≤ d [#permalink] New post 04 Feb 2018, 15:35
Expert's post
00:00

Question Stats:

100% (00:55) correct 0% (00:00) wrong based on 6 sessions


If the diameter (d) of a circle is an integer and \(6 cm\) \(\leq\) \(d\) \(\leq\) \(10 cm\), which could be the area of the circle?

A. \(36\pi cm^2\)

B. \(25\pi cm^2\)

C. \(14\pi cm^2\)

D. \(6\pi cm^2\)

E. \(3\pi cm^2\)


Kudo for the right solution and explanation
[Reveal] Spoiler: OA

_________________

Get the 2 FREE GREPrepclub Tests

1 KUDOS received
Manager
Manager
User avatar
Joined: 15 Jan 2018
Posts: 147
GMAT 1: Q V
Followers: 3

Kudos [?]: 174 [1] , given: 0

Re: If the diameter (d ) of a circle is an integer and 6 cm ≤ d [#permalink] New post 04 Feb 2018, 19:14
1
This post received
KUDOS
Firstly, let me just remark that problems by McGraw-Hill are generally terrible. So don't take them as a very accurate gauge of how the GRE works.

This one is not too bad though. When we find the area of circles, we don't really care about diameters; we care about radii. We could quickly eliminate 3 answer choices by thinking along these lines: If the diameter is an integer, then the radius must also be an integer, or end in .5. For example, if the diameter was 10, the radius must be 5, but if the diameter was 9, the radius would be 4.5. So the area, which is πr^2, should either be a perfect square (if the radius was an integer) or end in .25 (if the radius ended in .5). C, D, and E fulfill neither of those categories. So it's either A or B.

We've also been told that 6 ≤ d ≤ 10. We still don't care about d, so I'd replace it with 2r and we'd get 6 ≤ 2r ≤ 10. Dividing all three parts gets us 3 ≤ r ≤ 5. So the radius must be 3, 4, or 5, and the areas could be 9π, 16π, or 25π. So it's B.
_________________

-
-
-
-
-

Need help with GRE math? Check out our ground-breaking books and app.

Re: If the diameter (d ) of a circle is an integer and 6 cm ≤ d   [#permalink] 04 Feb 2018, 19:14
Display posts from previous: Sort by

If the diameter (d ) of a circle is an integer and 6 cm ≤ d

  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®.