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Color Switching 4x4 Grid Parity

1800SpecialistCombinatorics

67th NMO Selection Tests for JBMO

All the 16 squares of a $4 \times 4$ array are white. Define a *move* by selecting a rectangle $1 \times 3$ or $3 \times 1$ and switching the colors of each of its squares from white to black or from black to white. Is it possible that all squares turn black after a sequence of moves?
0 students attempted0% solvedRating 1800

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