ABCDE is a regular pentagon with F at its center. How many different quadrilaterals can be formed by joining 4 of the points A,B,C,D,E and F? Choose the correct option:  A) 12  B) 10  C) 5  D) 15  E) 20
The number of polygons with k sides that can be formed by joining them is nCk   for quadrilaterals k=4   it has 6 sides n=6   6C4=15   Answer is 15
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ABCDE is a regular pentagon with F at its center. How many different quadrilaterals can be formed by joining 4 of the points A,B,C,D,E and F?