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

 It is currently 29 Jun 2016, 22:08

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

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Six boys and six girls sit in a row at random.Find the

Author Message
Director
Joined: 03 Sep 2006
Posts: 879
Followers: 6

Kudos [?]: 566 [0], given: 33

Six boys and six girls sit in a row at random.Find the [#permalink]

Show Tags

22 Dec 2007, 22:04
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Six boys and six girls sit in a row at random.Find the probability that the boys and girls sit alternately.

A) 1/132

B) 1/462

C) 1/623

D) 1/231
CEO
Joined: 17 Nov 2007
Posts: 3580
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 485

Kudos [?]: 2802 [0], given: 359

Show Tags

23 Dec 2007, 02:35
Expert's post
B

P=2*6P6*6P6/12P12=2*6!*6!/12!=2*6*5*4*3*2/(12*11*10*9*8*7)=1/462
Manager
Joined: 16 Jan 2007
Posts: 73
Followers: 1

Kudos [?]: 16 [0], given: 0

Show Tags

23 Dec 2007, 02:36
The answer is 'B' i.e. 1/462.

Sample space = 12!

Boys can be seated alternately in 6! ways
Girls can be seated alternately in 6! ways

This can happen in 2 ways as the seats are even .
Likely events = 2* 6!*6!

Probability = Likely events/Sample space
= 2* 6! * 6! /12!
= 1/462
Display posts from previous: Sort by