Permutations & Combinations

Permutations care about order; combinations don't. With or without repetition, here are the formulas.

	With repetition	Without repetition
Permutation Order matters	$n^r$	${}_nP_r=\frac{n!}{(n-r)!}$
MS Excel formula	`PERMUTATIONA(n,r)`	`PERMUT(n,r)`
Combination Order does NOT matter	$\frac{(r+n-1)!}{r!(n-1)!}$	${}_nC_r=\frac{n!}{(n-r)!\,r!}$
MS Excel formula	`COMBINA(n,r)`	`COMBIN(n,r)`