MathDB
Random Permutation

Source:

January 5, 2009
probability

Problem Statement

Let S S be the set of permutations of the sequence 1,2,3,4,5 1, 2, 3, 4, 5 for which the first term is not 1 1. A permutation is chosen randomly from S S. The probability that the second term is 2 2, in lowest terms, is a/b a/b. What is a \plus{} b?
<spanclass=latexbold>(A)</span> 5<spanclass=latexbold>(B)</span> 6<spanclass=latexbold>(C)</span> 11<spanclass=latexbold>(D)</span> 16<spanclass=latexbold>(E)</span> 19 <span class='latex-bold'>(A)</span>\ 5 \qquad <span class='latex-bold'>(B)</span>\ 6 \qquad <span class='latex-bold'>(C)</span>\ 11 \qquad <span class='latex-bold'>(D)</span>\ 16 \qquad <span class='latex-bold'>(E)</span>\ 19