Permutations Formula
Also known as: nPr Formula, Arrangement Formula
P(n, r) = \frac{n!}{(n-r)!}
P(n,r) = n! / (n-r)!What It Calculates
Counts the number of ways to arrange r items from a set of n, where ORDER MATTERS.
variables
| Symbol | Name | Description |
|---|---|---|
| n | Total Items | Total number of items to choose from |
| r | Items Chosen | Number of items being arranged |
Worked Examples
1
P(5,3) = 5! / (5-3)! = 5! / 2!2
= 120 / 2 = 60Result: 60
Common Mistakes
Permutations = order matters. Combinations = order doesn't matter.
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#combinatorics#probability#counting