The difference between any two consecutive interior angles of a polygon is 5°. If the smallest angle is 120° , find the number of the sides of the polygon.
7
9
10
14
16
7
9
10
14
16
Charged up again to beat the beast 
The external angles of the Polygon 60, 55, 54 etc and sum of external angles is 360:
So, As per AP:
[2a + (n-1)d]n/2 = S
[2*60 + (n-1)(-5)]n/2 = 360
120n-5n^2+5n=720
n^2-25n-144=0
n^2-9n-16n-144=0
n=9, 16
Not sure how to pick 9 or 16. Brute Force?? Is there a shorter method?
