Description: Perimeter is the distance around the edge of a shape. Learn how to find the perimeter by adding up the side lengths of various shapes. Created by Sal Khan. When people use the word "perimeter" in everyday language, they're talking about the boundary of some area. Well, here, all the sides are the same, so the perimeter for this triangle is going to be 4 plus 4 plus 4, and whatever units this is. So what is the perimeter of this rectangle going to be?*Teacher Advisor is 100% free.