20 triangles have intersection
Source: 2019 China TST Test 4 P3
March 29, 2019
combinatoricsgeometrycombinatorial geometry
Problem Statement
points lie on the plane, such that no three points are collinear. Prove that one can divide the points into groups, with points in each group, such that the triangles ( in total) consist of three points in a group have a non-empty intersection.