Find all School-related info fast with the new School-Specific MBA Forum

It is currently 02 Oct 2014, 03:08

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

In a room filled with 7 people, 4 people have exactly 1

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Director
Director
avatar
Joined: 27 Jun 2005
Posts: 517
Location: MS
Followers: 2

Kudos [?]: 12 [0], given: 0

In a room filled with 7 people, 4 people have exactly 1 [#permalink] New post 13 Feb 2006, 10:22
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
In a room filled with 7 people, 4 people have exactly 1 friend in the room and 3 people have exactly 2 friends in the room. If two individuals are selected from the room at random, what is the probability that those two individuals are NOT friends?

5/21
3/7
4/7
5/7
16/21
VP
VP
avatar
Joined: 21 Sep 2003
Posts: 1071
Location: USA
Followers: 3

Kudos [?]: 31 [0], given: 0

 [#permalink] New post 13 Feb 2006, 14:33
Is it 16/21?

There can be only 2 groups possible among 7 of them:
Group1 : ABCD - Have of them exactly 1 friends
Group2 : EFG - Have exactly 2 friends

P(Both NOT friends) = 1 - P(Both friends) = 1 - [ P(two friends are from Group1) + P (two of them are from Group2)]

P(two of them have exactly 1 friend) = 4/7*1/6 -- Choose any of the 4 friends from Group1 and then choose HIS only freind

P (two of them have exactly 2 friends) = 3/7*2/6 -- Choose any of the 3 friends from Group2 and then choose one of his 2 freinds

P(Both NOT freinds) = 1 - { 4/42+6/42} = 16/21.

I may be wrong....
_________________

"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."

- Bernard Edmonds

Director
Director
avatar
Joined: 27 Jun 2005
Posts: 517
Location: MS
Followers: 2

Kudos [?]: 12 [0], given: 0

 [#permalink] New post 19 Feb 2006, 22:54
giddi77 wrote:
Is it 16/21?

There can be only 2 groups possible among 7 of them:
Group1 : ABCD - Have of them exactly 1 friends
Group2 : EFG - Have exactly 2 friends

P(Both NOT friends) = 1 - P(Both friends) = 1 - [ P(two friends are from Group1) + P (two of them are from Group2)]

P(two of them have exactly 1 friend) = 4/7*1/6 -- Choose any of the 4 friends from Group1 and then choose HIS only freind

P (two of them have exactly 2 friends) = 3/7*2/6 -- Choose any of the 3 friends from Group2 and then choose one of his 2 freinds

P(Both NOT freinds) = 1 - { 4/42+6/42} = 16/21.

I may be wrong....



you got it right OA is 16/21
  [#permalink] 19 Feb 2006, 22:54
    Similar topics Author Replies Last post
Similar
Topics:
In a room filled with 7 people, 4 people have exactly 1 dred 2 29 Jun 2007, 14:09
In a room filled with 7 people, 4 people have exactly 1 LM 12 21 May 2007, 23:24
In a room filled with 7 people, 4 people have exactly 1 amd08 2 17 Mar 2007, 17:16
In a room filled with 7 people, 4 people have exactly 1 shehreenquayyum 3 17 Jul 2006, 16:47
In a room filled with 7 people, 4 people have exactly 1 X & Y 7 23 Jun 2006, 19:38
Display posts from previous: Sort by

In a room filled with 7 people, 4 people have exactly 1

  Question banks Downloads My Bookmarks Reviews Important topics  


cron

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

Powered by phpBB © phpBB Group and phpBB SEO

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®.