Internal angles of an octagon: ACT Math Practice Question

Try this ACT math practice question on the internal angles of an octagon.

In a regular octagon, all $8$ interior angles are congruent. What is the measure of each interior angle of a regular octagon?

1. $\quad 22.5^{\circ}$
2. $\quad 45^{\circ}$
3. $\quad 120^{\circ}$
4. $\quad 135^{\circ}$
5. $\quad 150^{\circ}$

Choice D

Video explanation