MathDB
St Petersburg 2008 #7

Source:

July 23, 2011
combinatorics proposedcombinatorics

Problem Statement

A square with side 20082008 is broken into regions that are all squares with side 11. In every region, either 00 or 11 is written, and the number of 11's and 00's is the same. The border between two of the regions is removed, and the numbers in each of them are also removed, while in the new region, their arithmetic mean is recorded. After several of those operations, there is only one square left, which is the big square itself. Prove that it is possible to perform these operations in such a way, that the final number in the big square is less than 12106\frac{1}{2^{10^6}}.