Statistics & Probability
Intermediate

Permutations

Number of ordered arrangements of r items from n.

Formula

P(n,r)=n!(n−r)!P(n,r) = \frac{n!}{(n-r)!}

Variables

nTotal items
rChosen items

Example

Ways to arrange 2 of 4 people in order: P(4,2) = 4!/2! = 12.

Did You Know?

Permutations count ordered arrangements — there are 8×10⁵⁶ ways to shuffle a deck of 52 cards.

combinatoricspermutations