oriented graph hidden in convex polyhedra
Source: Romanian IMO TST 2005 - day 4, problem 2
April 23, 2005
Eulercombinatorics proposedcombinatorics
Problem Statement
On the edges of a convex polyhedra we draw arrows such that from each vertex at least an arrow is pointing in and at least one is pointing out.
Prove that there exists a face of the polyhedra such that the arrows on its edges form a circuit.
Dan Schwartz