MathDB
P10 [Combinatorics] - Turkish NMO 1st Round - 2001

Source:

April 20, 2014

Problem Statement

At each step, we are changing the places of exactly two numbers from the sequence 11, 22, 33, 44, 55, 66, 77. How many different arrangements can be formed after two steps?
<spanclass=latexbold>(A)</span> 88<spanclass=latexbold>(B)</span> 100<spanclass=latexbold>(C)</span> 120<spanclass=latexbold>(D)</span> 176<spanclass=latexbold>(E)</span> 441 <span class='latex-bold'>(A)</span>\ 88 \qquad<span class='latex-bold'>(B)</span>\ 100 \qquad<span class='latex-bold'>(C)</span>\ 120 \qquad<span class='latex-bold'>(D)</span>\ 176 \qquad<span class='latex-bold'>(E)</span>\ 441