Quote:
Originally Posted by nfotiu
Not sure what it would be called. But pretty sure the right formula would be 30*29*30*29*30*29*20*19*10
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You are off by a factor of 8 because you are using the permutation function instead of the choose function. The difference is that permutations can include duplicates since it doesn't take order into account.
So, someone picking player A then player B from a list of 30 players would not be the same as someone picking player B then player A.
Using the choose function, those two are identical, so aren't counted twice. This is why when picking 2 from a group, the choose function is half the permutation function:
30c2 = 435
30p2 = 870