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
6 points are available to make triangles.
A combination of any 3 will make a unique triangle so:
6C3 = 20
And hence the answer is option C.