Jim,

If I'm remembering correctly myself *g* Permutations means that order is significant (abc is different than bca), Combinations mean that order is not significant (abc == cba).

For 10 things taken 3 at a time there are 720 permutations n! / ( n - k )! but only 120 combinations. I never remember the formulas because I don't use them often enough. I got it from a google search on permutation and factorial at http://www.themathpage.com/aPreCalc/permutations-combinations.htm#comb

>I may be incorrect but my recollection of probability math indicated that the formula for number of possible combinations of 10 items taken 3 at a time without repeating is
>
>10 * 9 * 8 or 720.
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>This represents the fact that position one can be any one of 10 possible items, positiom can be any one of 9 (since 1 of the 10 is in pos 1) and finally pos 3 can be any one of 8 (since 2 of them are in pos 1 and 2).
>
>Am I incorrect, could you explain your formula?