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UKMT Junior Kangaroo, 2024

Combinatorics Difficulty 2.0 Junior Find the answer United Kingdom

Priya painted each of the nine squares shown black, white or grey. What is the smallest number of squares that she would need to repaint so that no two squares with a common side are painted in the same colour?

(A) $2$ (B) $3$ (C) $4$ (D) $5$ (E) $6$

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