Question

What is the perimeter of a regular octagon in which all sides have a length of 5 feet.

Answer 1

Perimeter = sum of all the sides.
A regular octagon has 8 sides. 
The length of each side = 5 ft.
One side = 5 ft.
Eight sides = 5 × 8 = 40 ft.

The perimeter of the octagon is 40 ft.

Answer 2

Octagons have 8 sides. If each side is 5 feet then the perimeter is 40 feet. You add up the sides.