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Topic: Homework question: permutations
Replies: 12   Last Post: Oct 21, 2001 8:04 PM

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Entropix

Posts: 40
Registered: 12/13/04
Re: Homework question: permutations
Posted: Oct 14, 2001 11:55 PM
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"Fred Galvin" <galvin@math.ukans.edu> wrote in message
news://Pine.LNX.4.21.0110132333410.20087-100000@titania.math.ukans.edu...
> On Sun, 14 Oct 2001, Effusive wrote:
>

> > "Fred Galvin" <galvin@math.ukans.edu> wrote in message
> > news://Pine.LNX.4.21.0110131534290.10973-100000@titania.math.ukans.edu...

> > > S_n is the group of all permutations of {1,2,...,n}.
> > >
> > > If n is an even number, the following probabilities are equal:
> > > (a) the probability that a random element of S_n has odd order;
> > > (b) the probability that a random element of S_{n+1} has odd order;
> > > (c) the probability of getting equal numbers of heads and tails in n
> > > independent tosses of a fair coin.

> >
> > ?? n = 2
> >
> > {1, 2} Probability a random element has odd order is 1/2
> >
> > n + 1 = 3
> >
> > {1, 2, 3} Probability a random element has odd order is 2/3

>
> How do you get 2/3?? There are 3! = 6 permutations of {1,2,3}; 3 of
> them have order 2 (the transpositions), and the other 3 have order 1
> or 3.
>
> Permutation Order
> (1)(2)(3) 1
> (1,2)(3) 2
> (1,3)(2) 2
> (1)(2,3) 2
> (1,2,3) 3
> (1,3,2) 3


Lol! Sorry. I read something wrong; I won't post when I'm tired anymore.

-- Entropix








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