M has at least 79 members - Iran NMO 2005 - Problem3
Source:
September 21, 2010
geometry3D geometryspherecombinatorics proposedcombinatorics
Problem Statement
In one galaxy, there exist more than one million stars. Let be the set of the distances between any of them. Prove that, in every moment, has at least members. (Suppose each star as a point.)