1

Part of 2001 Kurschak Competition

Problems(1)

Convex hull not a triangle

Source: Kürschák 2001, problem 1

3n-1

points are given in the plane, no three are collinear. Prove that one can select

2n

of them whose convex hull is not a triangle.

combinatorial geometrycombinatorics unsolvedcombinatorics