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Lusophon Mathematical Olympiad
2012 Lusophon Mathematical Olympiad
2
2
Part of
2012 Lusophon Mathematical Olympiad
Problems
(1)
painting houses on a nxn board
Source: Lusophon 2012 CPLP P2
8/29/2018
Maria has a board of size
n
×
n
n \times n
n
×
n
, initially with all the houses painted white. Maria decides to paint black some houses on the board, forming a mosaic, as shown in the figure below, as follows: she paints black all the houses from the edge of the board, and then leaves white the houses that have not yet been painted. Then she paints the houses on the edge of the next remaining board again black, and so on. a) Determine a value of
n
n
n
so that the number of black houses equals
200
200
200
. b) Determine the smallest value of
n
n
n
so that the number of black houses is greater than
2012
2012
2012
.
combinatorics
board