Question

How many sides does a regular polygon have if each exterior angle measures 20°?

a.
17 sides
b.
20 sides
c.
21 sides
d.
18 sides

Answer 1

the sum of the extrior angles always adds to 360
each exterior angle has to have a side to go with it

so
360/20=18 sides

answer is D

Answer 2

Sum of exterior angles of any polygon is 360 degrees.
Each exterior angle of a regular polygon = 360/n where n is the number of sides.
So, n = 360/20 = 18. Your answer is D


Hope this helps.