Get Outside! Measuring Side Lengths to Determine the Perimeter of Polygons

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Whether inside or outside the house, we travel different distances. We commute, we travel, we drive. We go to all sorts of places through straight paths or zigzags, or around something. The simplest act we do to go somewhere is to walk.

Walking is something common that almost all of us can and know how to do. Whether it is walking for leisure at the park or walking in a rush, it’s an activity that many of us take for granted. But it can also be a powerful learning tool for teaching!

Teaching the perimeter of polygons can be aided by an outside activity involving walking. Start off by telling your students that measurements are all around us, and the first thing we all have to do is get up and walk to find these measurements.

A recap of polygons

To recall, polygons are enclosed plane figures with three sides or more (poly = many). Polygons can be regular or irregular. As long as they are made of straight-line segments, that shape is considered a polygon. Some examples of polygons are triangles, quadrilaterals, and pentagons. There can also be complex polygons like stars and other multi-sided shapes. Since polygons are not necessarily regular, this is where you can introduce the idea that irregular polygons are all around us.

Measuring Side Lengths to Determine the Perimeter of Polygons is essential in third grade math development.

Practicing polygon shapes

Before taking your students outside for a walk, the first thing you need to do is solidify their knowledge of shapes, measuring sides, and then solving the perimeter of polygons. 

Make sure your students have a ruler, a piece of paper, and a pen, pencil, or marker for this practice session. If you haven’t checked it out already, see our article on creating a paper ruler with inch, half-inch, and quarter-inch intervals. Once all the materials are ready, have your students practice measuring small objects that are classified as a polygon. You can find many examples of these in the home or classroom.

For example, ask them to measure the length and width of an eraser, which looks like a rectangle. Once they have the measurements, ask for the perimeter of their measured object. This is the time that you can remind your students how to get the perimeter. In usual exercises, the measurement of the sides of polygons is already given and all they have to do is add them all up. But, with this practice of getting the measurement by themselves, it helps them understand how to get a perimeter reading.

Remind your kiddos that the perimeter is the sum of all measurements of the sides enclosing the polygon. It is the total measurement of the surrounding sides of the shape. Thus, if they forget to measure at least one side of the object, the perimeter will be incorrect. 

Head Outside

Now that your students have a foundation for measuring sides and solving for the perimeter, it’s time to take a walk outside. You can lead them outside the school or to the park, or just at the playground. Make sure that wherever you take them, there are plenty of examples of real-world polygons.

The materials advisable to be brought outside are a yardstick, a measuring tape, or any other measuring device that can measure long lengths. Also, don’t forget to bring water, sunblock, and umbrellas in case your students need them. 

To start the activity, find a rectangular or four-sided object. You may consider a sandbox or the building of the school. Ask them what shape is formed if you walk around that thing. They may answer different four-sided shapes or even identify it as an irregular quadrilateral. Tell them that the distance traveled going around that is the perimeter.

There are two ways you can instruct students to find the perimeter of real-life polygons: The first is the method of using measuring devices. This is a perfect opportunity to ask questions about which measuring device would be most suitable to do the job – a ruler, or a yardstick, for example. The second option is to use the method of measuring with your own footsteps.

Using the measuring stick or measure tape will find accurate data of measurements. If your students get confused about how to measure the sides using these tools, always go back to how to use a ruler. It is as simple as facing one end to 0 until finding what value the side stops on the other end of the segment. You can tell them to list as many polygons they find outside together with the perimeters of each polygon they find. They can work as individuals or have fun and work with their classmates. Make sure their findings include a variety of polygons and not just one or two kinds of shapes with the same number of sides. 

Moving to the second option of measuring sides and solving for the perimeter using footsteps, this method will truly be more active and physical. Tell them that they can be their own measuring device. You just simply walk and count your footsteps from the first end of the side until the last end of the segment. Remind them not to leave gaps between their footsteps and to try keep their steps as even as possible so the results are more accurate.

Once they know the measurements of all the sides in terms of their footsteps, they can add it all together and find the perimeter of real-life polygons in terms of their foot or step size. Since your students have different sizes of feet and lengths of stride, they will get different results to one another. It could be an exciting and interesting point of discussion in comparing lengths. 

This simple activity of going outside to find polygons is a helpful step in integrating the understanding that math is everywhere around us and not just in the classroom. It’s a fantastic way to open your kiddos’ thinking to finding math in everyday scenarios. 

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Before You Leave…

We hope these tips and activities will give you a good idea of how to help your students get the hang of measuring the side lengths to determine the perimeter of polygons. If you’re looking for more math materials for children of all ages, be sure to sign up for our email (you’ll receive lots of free content), sign up for a membership at MathTeacherCoach, and/or take a look at our blog where you’ll find lots of amazing resources that will help you organize successful yet fun classes all kids will enjoy. If you liked this lesson, be sure to check out this article on Creating a Ruler with 1/4, 1/2 and 1-inch Intervals!

Image Sources

Children walking

Shapes

Stationery

Playground

Footprints