Suppose you have three identical prisms with congruent equilateral triangles as the end-polygons. Suppose you attach them by the rectangular faces so they are perfectly aligned. There will be some large faces created by two or more co-planar faces of the individual prisms: count each such large face as one. Given that, how many faces does the resultant solid have\nOptions:\n(A)  4\n(B)  9\n(C) 6\n(D)  10\n(E)  12 OK. Let's think. Some random thoughts first:
User
To arrange them as described I did as follows on my scratch paper (see the file attached), where I counted 4 sides and added top and bottom, hence 4+2 = 6. The answer: (C).
Assistant