MathDB
A border separates a black square from a white square

Source: CentroAmerican 2004

December 10, 2010
geometryrectanglecombinatorics proposedcombinatorics

Problem Statement

In a 10×1010\times 10 square board, half of the squares are coloured white and half black. One side common to two squares on the board side is called a border if the two squares have different colours. Determine the minimum and maximum possible number of borders that can be on the board.