4 colours in a 41x5 chessboard
Source: 15th -a QEDMO problem 2 (19. - 22. 10. 2017) https://artofproblemsolving.com/community/c1512515_qedmo_2005
May 29, 2021
ColoringChessboardcombinatoricscombinatorial geometry
Problem Statement
Markers in the colors violet, cyan, octarine and gamma were placed on all fields of a chessboard. Show that there are four squares of the same color that form the vertices of a rectangle whose edges are parallel to those of the board.