Questions about the world of GMAT Math from other sources and general math related questions.
riyakhilnani7
Forum Guests
 
Posts: 3
Joined: Mon May 28, 2012 3:35 am
 

permutations with restrictions question

by riyakhilnani7 Sat Sep 22, 2012 5:44 am

What is the rationale behind the answer to this question

There are 6 children, 3 boys and 3 girls. They will be lined up single file for a photo, alternating genders. how many arrangements of children are possible?

Answer: 3! x 3! x 2 = 72
garima_aries01
Students
 
Posts: 9
Joined: Tue Jun 29, 2010 8:52 pm
 

Re: permutations with restrictions question

by garima_aries01 Sat Sep 22, 2012 7:25 am

riyakhilnani7 Wrote:There are 6 children, 3 boys and 3 girls. They will be lined up single file for a photo, alternating genders. how many arrangements of children are possible



B = boy
G = girl

BGBGBG ==>3 Bs can be placed in 3! ways
Likewise 3 Gs can be placed in 3! ways
And the sequence can be GBGBGB too so
2x3!x3!
tim
Course Students
 
Posts: 5665
Joined: Tue Sep 11, 2007 9:08 am
Location: Southwest Airlines, seat 21C
 

Re: permutations with restrictions question

by tim Wed Sep 26, 2012 11:37 am

thanks! let us know if there are any further questions on this one..
Tim Sanders
Manhattan GMAT Instructor

Follow this link for some important tips to get the most out of your forum experience:
https://www.manhattanprep.com/gmat/forums/a-few-tips-t31405.html