Convex polyhedron (again no geometry)
Source: German Math. Competition BWM 2002, 2nd round, problem 3
November 19, 2005
geometryinductioncombinatorics proposedcombinatorics
Problem Statement
Given a convex polyhedron with an even number of edges.
Prove that we can attach an arrow to each edge, such that for every vertex of the polyhedron, the number of the arrows ending in this vertex is even.