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Topic: Permutation problems
Replies: 13   Last Post: Aug 12, 2013 2:23 PM

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Ben Brink

Posts: 196
From: Rosenberg, TX
Registered: 11/11/06
RE: Permutation problems
Posted: May 19, 2012 4:34 AM
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Mahesh,
Before dealing with that, how did you find 23! permutations not containing "fish"? Thanks.
Ben


> Date: Sat, 19 May 2012 02:35:41 -0400
> From: discussions@mathforum.org
> To: discretemath@mathforum.org
> Subject: Re: RE: Permutation problems
>
> I could make some progress after your reply. I thought of doing it other way round. So now the sets are:
> A: Contain fish |A|=23!
> B: Contain rat |B|=24!
> C: Contain bird |C|=23!
> A n B: 21!
> A n C: 20!
> B n C: 21!
> A n B n C: 18!
>
> A' n B' n C'= Total permutations - (A u B u C)
> = 26!-(23! + 24! + 23! - 21! - 20! - 21! +18!)
> =4.0261.... * 10 ^ 26
> Let me know if this is correct.
> Thank you.





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