MathDB
coloring 1 of 10 colors of circle May Olympiad (Olimpiada de Mayo) 2018 L2 P5

Source:

September 24, 2021
combinatoricsColoringcombinatorial geometry

Problem Statement

Each point on a circle is colored with one of 1010 colors. Is it true that for any coloring there are 44 points of the same color that are vertices of a quadrilateral with two parallel sides (an isosceles trapezoid or a rectangle)?