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Printsmc
counting and probability senior
Problem
Several figures can be made by attaching two equilateral triangles to the regular pentagon ABCDE in two of the five positions shown. How many non-congruent figures can be constructed in this way? 
(A)
(B)
(C)
(D)
Solution
Place the first triangle. Now, we can place the second triangle either adjacent to the first, or with one side between them, for a total of
Final answer
B