Coloring a square grid
Source:
December 28, 2006
probabilitygeometryrectanglenumber theoryrelatively prime
Problem Statement
Each unit square of a 3-by-3 unit-square grid is to be colored either blue or red. For each square, either color is equally likely to be used. The probability of obtaining a grid that does not have a 2-by-2 red square is , where and are relatively prime positive integers. Find .