Probability & Combinatorics
Basic

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

P(5,2) = 5!/3! = 20

Did You Know?

Order matters in permutations, unlike combinations.

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