Aro 2011 10-8
Source:
April 28, 2011
invariantgraph theorycombinatorics proposedcombinatorics
Problem Statement
A board is divided into corner-shaped figures of three cells. Prove that it is possible to mark one cell in each figure such that each row and each column will have the same number of marked cells.I. Bogdanov & O. Podlipsky