MathDB
Math Prize 2016 Problem 5

Source:

September 12, 2016
Math Prize for Girls

Problem Statement

A permutation of a finite set SS is a one-to-one function from SS to SS. A permutation PP of the set {1,2,3,4,5}\{ 1, 2, 3, 4, 5 \} is called a W-permutation if P(1)>P(2)<P(3)>P(4)<P(5)P(1) > P(2) < P(3) > P(4) < P(5). A permutation of the set {1,2,3,4,5}\{1, 2, 3, 4, 5 \} is selected at random. Compute the probability that it is a W-permutation.
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