MathDB
Turkey NMO 2007 1st Round - P24 (Combinatorics)

Source:

October 5, 2012

Problem Statement

The integers from 11 to nn are arranged along a circle such that each number is a multiple of difference of its adjacents. For which nn below such an arrangement is possible?
<spanclass=latexbold>(A)</span> 5<spanclass=latexbold>(B)</span> 6<spanclass=latexbold>(C)</span> 7<spanclass=latexbold>(D)</span> 9<spanclass=latexbold>(E)</span> 13 <span class='latex-bold'>(A)</span>\ 5 \qquad<span class='latex-bold'>(B)</span>\ 6 \qquad<span class='latex-bold'>(C)</span>\ 7 \qquad<span class='latex-bold'>(D)</span>\ 9 \qquad<span class='latex-bold'>(E)</span>\ 13