Permutations and Combinations Formula Reference
| Repeats allowed | No Repeats | |
|---|---|---|
| Permutations (order matters): | n^r | n!/(n − r)! |
| Combinations (order doesn’t matter): | (r + n − 1)!/r!(n − 1)! | n!/r!(n − r)! |
| Repeats allowed | No Repeats | |
|---|---|---|
| Permutations (order matters): | n^r | n!/(n − r)! |
| Combinations (order doesn’t matter): | (r + n − 1)!/r!(n − 1)! | n!/r!(n − r)! |