Which of the following is not the the size of an exterior angle of a regular polygon?
A
15o
B
18o
C
20o
D
21o
Verified Correct Answer: D.
Step-by-Step Mathematical Solution
The size of an exterior angle = \(\frac{360}{n}\)
From the options, all options can perfectly divide 360^\circ, except 21^\circ.
Source: Myschool Past Questions Archive (Record #26507)