Difference between revisions of "2012 AMC 10A Problems/Problem 20"
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Revision as of 22:48, 8 February 2012
Problem 20
A 
x square is partitioned into 
unit squares. Each unit square is painted either white or black with each color being equally likely, chosen independently and at random. The square is then rotated 
clockwise about its center, and every white square in a position formerly occupied by a black square is painted black. The colors of all other squares are left unchanged. What is the probability the grid is now entirely black?
