Re: Combinatorica questions!!!
- To: mathgroup at smc.vnet.net
- Subject: [mg20606] Re: [mg20499] Combinatorica questions!!!
- From: Rob Pratt <rpratt at email.unc.edu>
- Date: Tue, 2 Nov 1999 02:35:36 -0500
- Sender: owner-wri-mathgroup at wolfram.com
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. > > > >