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CEMC Gauss (Grade 7), 2011

Combinatorics Difficulty 3.0 AMC 10/12 Find the answer Canada

From the figure shown, three of the nine squares are to be selected. Each of the three selected squares must share a side with at least one of the other two selected squares. In how many ways can this be done?

(A) $19$ (B) $22$ (C) $15$ (D) $16$ (E) $20$

Figure for this problem

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