Colorful combo geo
Source: IMSC 2023 Mock IMO P5
July 13, 2023
combinatorics
Problem Statement
In the plane, points are chosen such that no three points lie on the same line. Each of the points is coloured red or blue such that each triangle formed by three distinct red points contains at least one blue point.
What is the largest possible number of red points?Proposed by Art Waeterschoot, Belgium