a rectangle is formed of 3 × 7 by 21 bw pieces, vertices of rectangle
Source: 2012 Cuba MO 1.4
September 18, 2024
geometrycombinatorial geometrycombinatoricsColoringrectangle
Problem Statement
With pieces, some white and some black, a rectangle is formed of . Prove that there are always four pieces of the same color located at the vertices of a rectangle.