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by solankijignesh » Sat Feb 13, 2010 2:13 am
gmatnmein2010 wrote:ABCDE is a regular pentagon with F at its center. How many different triangles can be formed by joining 3 of the points A,B,C,D,E and F?
(A) 10
(B) 15
(C) 20
(D) 25
(E) 30
total 6 points and 3 points needed to make a triangle. so total triangles 6C3.
Any 3 points will make same triangle i.e. ABC, BAC, CAB
so total no of different triangles are: 6C3 / 3 = 20

whats the OA? is this approach correct? i am still a beginner...
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by thephoenix » Sat Feb 13, 2010 2:23 am
to make triangles a combination of any 3 point is enough there are 6 points in total;so
6C3 = 20
IMO C
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