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

It is currently 23 Jul 2014, 20:59

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

Seven people , two of them couples , are seated randomly in

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
CEO
CEO
avatar
Joined: 15 Aug 2003
Posts: 3470
Followers: 59

Kudos [?]: 657 [0], given: 781

Seven people , two of them couples , are seated randomly in [#permalink] New post 08 Oct 2003, 02:28
Seven people , two of them couples , are seated randomly in a row of 7 chairs. Whats the probability that the none of the couples are seated together?
Intern
Intern
avatar
Joined: 03 May 2003
Posts: 28
Followers: 0

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

Re: Probability...Couples [#permalink] New post 08 Oct 2003, 12:54
praetorian123 wrote:
Seven people , two of them couples , are seated randomly in a row of 7 chairs. Whats the probability that the none of the couples are seated together?


Total ways to seat 7 people = 7! = 5040
Ways that the couple are not together = 7! - (6!*2!) =
5040 - 1440 = 3600

couple not together/total = 3600/5040 = 360/504 = 5/7
CEO
CEO
avatar
Joined: 15 Aug 2003
Posts: 3470
Followers: 59

Kudos [?]: 657 [0], given: 781

Re: Probability...Couples [#permalink] New post 08 Oct 2003, 13:29
Quote:
Total ways to seat 7 people = 7! = 5040
Ways that the couple are not together = 7! - (6!*2!) =
5040 - 1440 = 3600
couple not together/total = 3600/5040 = 360/504 = 5/7


Ok, i get a different answer..but i am not real good a probability either..so please check my work
All couples together => total permutations 5! ( 2 couples and 3 kids)
one couple can be seated together in => 2 ! ways
second couple can be seated together in => 2 ! ways
Both the couples can be seated in together => 2! ways

So total = 5! * 2! * 2! * 2! = 6!

i get => 7! - 6! / 7! = 5040-720 / 5040 = 4320 / 5040 = 432 /504


thanks
praetorian

Last edited by Praetorian on 08 Oct 2003, 15:49, edited 1 time in total.
Intern
Intern
avatar
Joined: 03 May 2003
Posts: 28
Followers: 0

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

Re: Probability...Couples [#permalink] New post 08 Oct 2003, 15:27
exy18 wrote:
praetorian123 wrote:
Seven people , two of them couples , are seated randomly in a row of 7 chairs. Whats the probability that the none of the couples are seated together?


Total ways to seat 7 people = 7! = 5040
Ways that the couple are not together = 7! - (6!*2!) =
5040 - 1440 = 3600

couple not together/total = 3600/5040 = 360/504 = 5/7


I solved the above as if there was only 1 couple.

With 2 couples - the ways that they are not together = 7! - (6!*2!*2!)
=5040 - 2880 = 2160

2160/5040 = 216/504 ??? not sure if this is correct either ??
SVP
SVP
User avatar
Joined: 30 Oct 2003
Posts: 1798
Location: NewJersey USA
Followers: 3

Kudos [?]: 29 [0], given: 0

GMAT Tests User
 [#permalink] New post 08 Jan 2004, 08:05
7 people with two couple means 4+3 people
If they all the couple are seated together then
C1 C2 S1 S2 S3
combinations are 2*2*5!
Probability that none are seated together = 1 - 2*2*5!/7! = 38/42
  [#permalink] 08 Jan 2004, 08:05
    Similar topics Author Replies Last post
Similar
Topics:
9 people, including 3 couples, are to be seated in a row of chillpill 4 16 Apr 2006, 18:12
Two couples and a single person must be randomly seated in a vikramm 3 09 Oct 2005, 08:26
9 people, including 3 couples, are to be seated in a row of mbassmbass04 17 11 Apr 2005, 04:45
Two couples and one single person are seated at random in a iostrovsky 5 10 Oct 2004, 14:31
Two couples and one single person are seated at random in a srijay007 8 19 Sep 2004, 21:14
Display posts from previous: Sort by

Seven people , two of them couples , are seated randomly in

  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®.