Perimeter of Polygons

Pre-Algebra · Axiom Academy

The distance around any polygon is just the sum of its sides — and when every side is equal, that sum becomes a multiplication. 1. Perimeter Is the Walk Around Picture walking the edge of a polygon, one side at a time, counting the length of each side as you pass it. By the time you arrive back at your starting corner, the running total in your head is the perimeter. Watch a dot make that trip below — every side it crosses is added to the total. Add the length of every side, all the way around A regular polygon has every side the same length. Adding the same number over and over is exactly what multiplication does — so instead of adding each side, you can multiply one side length by the number of sides. Watch the six equal sides of this hexagon collect into a single product. where n is the number of sides and s is the length of one side. A regular hexagon with each side 4 cm: — the same answer as 4+4+4+4+4+4 , found in one step. If the sides are not all equal, there is no shortcut — fall back to adding each side once, just as in Step 1. You have seen that a polygon's perimeter is simply the distance traced all the way around it — and how equal sides turn that sum into a quick multiplication. Scroll up to revisit either step.

This is the written version of the interactive lesson above. See the full Pre-Algebra course.