MathDB

10

Part of 2001 National Olympiad First Round

Problems(1)

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

Source:

4/20/2014
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=′latex−bold′>(A)</span> 88<spanclass=′latex−bold′>(B)</span> 100<spanclass=′latex−bold′>(C)</span> 120<spanclass=′latex−bold′>(D)</span> 176<spanclass=′latex−bold′>(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