Re: Re: Combinatorica questions!!!
- To: mathgroup at smc.vnet.net
- Subject: [mg20616] Re: [mg20606] Re: [mg20499] Combinatorica questions!!!
- From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
- Date: Thu, 4 Nov 1999 02:13:31 -0500
- Sender: owner-wri-mathgroup at wolfram.com
It does seem rather trivial when you look at it the right way. It would have been easier to see if the problem referred the the king, not a rook :) -- > From: Rob Pratt <rpratt at email.unc.edu> To: mathgroup at smc.vnet.net > Date: Tue, 2 Nov 1999 02:35:36 -0500 > To: mathgroup at smc.vnet.net > Subject: [mg20616] [mg20606] Re: [mg20499] Combinatorica questions!!! > > An approach to problem 1 that is simpler than those already given is to > recognize that each path consists of a sequence of 14 moves, 7 of them to > the RIGHT one space and 7 of them UP one space. Hence a path is uniquely > determined by specifying which 7 of the 14 moves are RIGHT (the rest are > UP). We are choosing 7 objects from among 14 positions, so the answer is > > Binomial[14,7]=3432 > > Rob Pratt > Department of Operations Research > The University of North Carolina at Chapel Hill > > rpratt at email.unc.edu > > http://www.unc.edu/~rpratt/ > > On Wed, 27 Oct 1999, Keren Edwards wrote: > >> Hi all!! >> >> 2 different questions: >> >> 1. how many ways does a castle have to reach from the bottom left side >> corner >> of a chess board to the upper right corner of the board if he can >> move right >> and up only? >> >> >> >> 2. you have 8 red identical balls, 9 purple identical balls and 7 white >> identical ones. >> a. How many ways can you choose 10 balls with no matter to the >> order of the balls? >> b. How many ways can you choose 10 balls with no matter to the >> order of the balls, if each color must >> be chosen once at least? >> >> >> >> Many thanx. >> >> >> >> > > >