Re: A Question about Combinatorica

*To*: mathgroup at smc.vnet.net*Subject*: [mg102684] Re: [mg102627] A Question about Combinatorica*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Tue, 18 Aug 2009 06:11:01 -0400 (EDT)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*References*: <200908170804.EAA27022@smc.vnet.net>*Reply-to*: murray at math.umass.edu

Sorry, but your questions is unclear. There are 5!, that is, 120, permutations of a list of length 5. And that is what Permutations and Combinatorica`MinimumChangePermutations` both give you. What does 60 have to do with it? Marwa Abd El-Wahaab wrote: > Dear Sir, > I have a question about having five letters like {A, B, C, D, E}. In order > to get all possibilities, we have 5! possible cases like ABCDE, > EABCD,.......etc > > The number of these possibilities are 120. How and why this number becomes > 60 by dividing by 2 ? > > What are 60 possibilities & how extract them from 120? > > I used this function to get 120: > > MinimumChangePermutations[{A,B,C,D,E}] > > What should I do after this to get 60? > > Thanks too much > > I really need your help > > *Marwa Ali Abd El Wahaab* > *Teaching Assistant* > Faculty of Engineering > Mansoura University > > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305

**References**:**A Question about Combinatorica***From:*Marwa Abd El-Wahaab <m.a.elwahaab@gmail.com>