The number of diagonals of a polygon of n sides is given by the formula c=n(n-3)/2. If a polygon has twice as many diagonals as sides, how many sides does it have?  Choose one:
A) 3	B) 5	C) 6	D) 7	E) 8

Rationale: c = n ( n - 3 ) c = 2 * n 2 n = n ( n - 3 ) = > 2 = n - 3 = > n = 5 answer b
Answer: B