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Re: Combinatorica questions!!!

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  • Subject: [mg20606] Re: [mg20499] Combinatorica questions!!!
  • From: Rob Pratt <rpratt at>
  • Date: Tue, 2 Nov 1999 02:35:36 -0500
  • Sender: owner-wri-mathgroup at

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


Rob Pratt
Department of Operations Research
The University of North Carolina at Chapel Hill

rpratt at

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.

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