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saurabhbanerjeeiimk
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Post subject: Forth Edition Word Translations, Combinometrics Pg 76 Q15  Posted: Fri Dec 09, 2011 1:09 am |
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The question reads as "Gordon buys 5 dolls for his 5 nieces."
Why is 4!/2!= 12 being explained as the ways in which the youngest niece gets the GI doll. The calculation is based on the dolls OTHER than the GI doll.
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tim
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Post subject: Re: Forth Edition Word Translations, Combinometrics Pg 76 Q15 Posted: Tue Dec 13, 2011 2:42 am |
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| ManhattanGMAT Staff |
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Location: Southwest Airlines, seat 21C
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Exactly. If we want to calculate the number of ways to give the GI doll to the youngest niece, we give her the GI doll first and then calculate all the ways to give out the other dolls as well. Every one of these possibilities is different, but they all give the GI doll to the youngest niece..
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Tim Sanders
Manhattan GMAT Instructor
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saurabhbanerjeeiimk
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Post subject: Re: Forth Edition Word Translations, Combinometrics Pg 76 Q15 Posted: Thu Dec 22, 2011 10:26 am |
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Not clear yet :(
Q1. As per the answer, AFTER the GI doll is given to niece E, the combination for the 4 remaining dolls is calculated for the OTHER 4 nieces, i.e neice E is excluded from the 4 nieces. Which would imply that the 12 ways are for the 4 nieces.
Q2. Is this question based on the "Glue method"
If your answer to Q2 is Yes, then kindly explain the calculation related to the 4 remaining dolls (by correlating it to the Glue method)
Thanks a ton an advance!
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tim
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Post subject: Re: Forth Edition Word Translations, Combinometrics Pg 76 Q15 Posted: Sat Dec 31, 2011 1:47 pm |
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Location: Southwest Airlines, seat 21C
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EXACTLY! There are 12 ways we can give the dolls out to the other 4 neices. You’re right; it sounds like you agree with me 100%. Unfortunately that means I’m not seeing where your question lies. This problem does not need to use the glue method, to answer your second question..
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Tim Sanders
Manhattan GMAT Instructor
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pranabiitkgp
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Post subject: Re: Forth Edition Word Translations, Combinometrics Pg 76 Q15 Posted: Mon Feb 20, 2012 5:49 am |
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Hi ,
I dont understand the slot method very well , but easy with permutation .
So can this be explained as bellow -
Is it a permutation of picking 5 out of 5 where 2 are same - 5P2/!2 ?
If this is correct so can it be like if there were 3 sisters instead of 5 , with all other condition intact ,the solution would have been -
Total # of ways to distribute SSEGT among 3 sisters (without restriction) is 5P3/!2 = 15;
The # of ways when the youngest niece gets G is: 4P2/!2 = 6 (give G to youngest and then distribute SSET among 2 sisters).
So, # of ways when youngest niece doesn't get G is:15-6 = 9 .
Please explain for better understanding . Thanks.
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pranabiitkgp
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Post subject: Re: Forth Edition Word Translations, Combinometrics Pg 76 Q15 Posted: Mon Feb 20, 2012 5:52 am |
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a typo correction to my previous post -
Is it a permutation of picking 5 out of 5 where 2 are same - 5P5/!2
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jnelson0612
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Post subject: Re: Forth Edition Word Translations, Combinometrics Pg 76 Q15 Posted: Sun Feb 26, 2012 9:24 pm |
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| ManhattanGMAT Staff |
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pranabiitkgp wrote: a typo correction to my previous post -
Is it a permutation of picking 5 out of 5 where 2 are same - 5P5/!2 Correct! So your calculation is: 5! 2!1!1!1!
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Jamie Nelson
ManhattanGMAT Instructor
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