TOT 279 1990 Autumn A S4 10 red and 10 white points
Source:
June 8, 2024
geometrycombinatoricscombinatorial geometry
Problem Statement
There are points in the plane and no three of them are collinear. Of these points are red while the other are blue. Prove that there exists a straight line such that there are red points and blue points on either side of this line.(A Kushnirenko, Moscow)