Permutations & Combinations

nPr and nCr for counting problems.

Enter values

n (total)

r (chosen)

—

nPr = n!/(n−r)!; nCr = n!/(r!(n−r)!)

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When do I use permutations vs combinations?+

Use permutations when order matters (e.g. race finishes) and combinations when it does not (e.g. picking a committee).

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