Permutations

Definition: Combinatorics is a branch of mathematics about the selection and deployment of elements of a set based on some conditions

Selected (or available) group of elements called compounds

Permutations

Definition: Permutations of the different elements are called finite ordered set (that is, such sets that specify the order of elements) can be removed from a set containing elements (if all elements of a given set of different — get permutations without repetitions, but if in the given set elements may be repeated, then get the permutations with repetitions)

Formula for the number of permutations

Without repetition

where (read "n factorial")

For (by definition)

Example. The number of different six-digit numbers can be formed from the digits without repeating the numbers in one number equal to

With repetitions

where

Example.The number of different six-digit numbers can be formed from three twos, two sevens and one five

(considered )

Chapter:
Chapter: Combinatorics
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