MathDB
Putnam 1979 A4

Source:

April 8, 2022
college contests

Problem Statement

Let AA be a set of 2n2n points in the plane, no three of which are collinear. Suppose that nn of them are colored red and the remaining nn blue. Prove or disprove: there are nn closed straight line segments, no two with a point in common, such that the endpoints of each segment are points of AA having different colors.