WAEC 2020 · Paper 1 · Q29

Each interior angle of a regular polygon is $168^\circ$ . Find the number of sides of the polygon.

Worked solution (try it first)

An interior angle and its exterior angle add up to $180^\circ$ , so each exterior angle is $180^\circ - 168^\circ = 12^\circ$ .
The exterior angles add up to $360^\circ$ , so the number of sides is $360 \div 12 = 30$ , option A.