It is currently 20 Oct 2017, 09:52

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If a point is arbitrarily selected inside a circle of radius

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

VP
VP
User avatar
Status: Been a long time guys...
Joined: 03 Feb 2011
Posts: 1377

Kudos [?]: 1676 [0], given: 62

Location: United States (NY)
Concentration: Finance, Marketing
GPA: 3.75
GMAT ToolKit User Premium Member
If a point is arbitrarily selected inside a circle of radius [#permalink]

Show Tags

New post 26 Oct 2012, 21:20
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

70% (00:48) correct 30% (00:53) wrong based on 60 sessions

HideShow timer Statistics

If a point is arbitrarily selected inside a circle of radius R, what is the probability that the distance from this point to the center of the circle will be greater than R/2 ?

A. 1/2
B. 3/4
C. 7/8
D. 1/4*R^2
E. 3/4*R^2
[Reveal] Spoiler: OA

_________________

Prepositional Phrases Clarified|Elimination of BEING| Absolute Phrases Clarified
Rules For Posting
www.Univ-Scholarships.com


Last edited by Marcab on 26 Oct 2012, 23:31, edited 1 time in total.

Kudos [?]: 1676 [0], given: 62

Intern
Intern
avatar
Joined: 02 Feb 2012
Posts: 29

Kudos [?]: 14 [0], given: 35

GPA: 4
Re: If a point is arbitrarily selected inside a circle of radius [#permalink]

Show Tags

New post 27 Oct 2012, 00:23
Area of circle with radius R, A1 = 2*pi*(R)^2
Area of circle with radius R/2, A2 = 2*pi*(R/2)^2

Implies, A1/A2 = 4/1

The area of the circle excluding the area of circle with radius R/2 is 3 times more..

Hence the probability will be 3/4

Kudos [?]: 14 [0], given: 35

Director
Director
User avatar
Status: Done with formalities.. and back..
Joined: 15 Sep 2012
Posts: 636

Kudos [?]: 653 [0], given: 23

Location: India
Concentration: Strategy, General Management
Schools: Olin - Wash U - Class of 2015
WE: Information Technology (Computer Software)
GMAT ToolKit User Premium Member Reviews Badge
Re: If a point is arbitrarily selected inside a circle of radius [#permalink]

Show Tags

New post 27 Oct 2012, 00:41
1
This post was
BOOKMARKED
Marcab wrote:
sorry....its R/2.
its been corrected in the original post.

Great now it makes sense :)
Basically in the question we are looking for probability of point lying in Green region in the attached figure.

Since the radius of Grean Circle is R and radius of red circle is R/2. Hence the area of greeen region =
\(pi R^2 - pi (r/2)^2\)
\(= 3/4 pi R^2\)

Also area of circle with radius R\(= pi R^2\)
Hence probability of point lying in green region =\(3/4 pi R^2 / pi R^2\)
= 3/4

Hence Ans B it is.

Hope it helps.
Attachments

circles.png
circles.png [ 15.76 KiB | Viewed 1513 times ]


_________________

Lets Kudos!!! ;-)
Black Friday Debrief

Kudos [?]: 653 [0], given: 23

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 16633

Kudos [?]: 273 [0], given: 0

Premium Member
Re: If a point is arbitrarily selected inside a circle of radius [#permalink]

Show Tags

New post 15 Aug 2017, 20:11
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Kudos [?]: 273 [0], given: 0

Re: If a point is arbitrarily selected inside a circle of radius   [#permalink] 15 Aug 2017, 20:11
Display posts from previous: Sort by

If a point is arbitrarily selected inside a circle of radius

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.