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?	Pick one
A) 3
B) 5
C) 6
D) 7
E) 8
c=n(n-3)   c=2*n   2n=n(n-3)   =&gt;2=n-3   =&gt;n=5   Answer 5
<result>B</result>
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?