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Permutation Formula


Date: 23 Apr 1995 06:27:14 -0400
From: Sam Grech
Subject: Choose formula

I can't for the life of me remember a particular formula.  It's the formula
for calculating the total possible number of ways to choose 'r' objects out 
of a total 'n'  objects. I know it looks something like:

p (n-r)
  -----
   n+r2   - I know this is really far off but maybe you
            can tell from this which formula I mean....

By the way, it should not count repeated selections that are in a different 
order [ie: if you choose 2 objects out of a possible 'n' numbers, (1,2) and 
(2,1) would only count as one possibility]. 

Any help you could give would be appreciated.

Sam Grech


Date: 23 Apr 1995 11:33:47 -0400
From: Dr. Ken
Subject: Re: Choose formula

Hello there!

Here's the formula you're looking for:

                  n!
n choose p  = -----------
               p! (n-p)!

Enjoy!

-K
    
Associated Topics:
High School Permutations and Combinations

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