Find the number of ways to arrange r items out of a set of n, where the order matters.
Counts ordered selections — choosing a 1st, 2nd and 3rd place winner from a group is a permutation problem.
nPr: n! ÷ (n−r)!
How is a permutation different from a combination?
A permutation cares about order — 1st, 2nd, 3rd place. A combination does not — it is just picking a group of 3, no matter the order. Permutations always give a bigger or equal count.