JAMB 2011 · UTME · Q27

What is the size of each interior angle of a 12-sided regular polygon?

Worked solution (try it first)

The exterior angles add up to $360^\circ$ , so each exterior angle of a regular 12-sided polygon is $360^\circ \div 12 = 30^\circ$ .
The interior angle is $180^\circ - 30^\circ = 150^\circ$ , option B.