I once read a very good explanation for the n! factor in the combinations formula but I can't find it. Can someone state the reason for it clearly please.(adsbygoogle = window.adsbygoogle || []).push({});

( N) = N!/n!/(N-n)!

( n)

The N!/(N-n)! comes about because there are that many ways to choose n things from N. N for the first, N-1 for the second, ... N-n+1 for the nth. So far so good.

There is a clear explanation for why this has 'double counted' and the n! term fixes it up.

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# N! term in formula for combinations

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