Tuesday, December 16, 2008

Permutations and Combinations - Some Results

1. if n items are arranged in a row, then the number of wasys in which they can be rearranged so that no one of them occupies the place assigned to it (all wrongly placed), is

n![1 - 1/1! + 1/2! - 1/3! +...+(-1)n(1/n!)]

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