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Prime Factor (Posted on 2006-05-12) Difficulty: 4 of 5
Determine the largest 3 - digit prime factor of 2000 C 1000.

n C r denotes the number of combinations of n things taking r at a time.

No Solution Yet Submitted by Ravi Raja    
Rating: 2.5000 (2 votes)

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Some Thoughts re: What am I missing? | Comment 4 of 8 |

Steve,
  I did the same thing initially. If you choose 1000 of 2000 items, and the order that you choose the items matters then the equation is:

n! / r!. 


However, if the order does not matter, (1,2 is the same as 2,1) then the equation becomes:


n! / (r! * (n-r)!)


  Posted by Leming on 2006-05-12 12:44:16
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