IMO Shortlist 1992 problem 4

  Avg: 0.0
  Avg: 0.0
Dodao/la: arhiva
April 2, 2012
Consider 9 points in space, no four of which are coplanar. Each pair of points is joined by an edge (that is, a line segment) and each edge is either colored blue or red or left uncolored. Find the smallest value of \,n\, such that whenever exactly \,n\, edges are colored, the set of colored edges necessarily contains a triangle all of whose edges have the same color.
Source: Međunarodna matematička olimpijada, shortlist 1992