Chalk Up Polygon Perimeters!

By third grade, students have a basic understanding of geometric shapes. They learn how to describe polygons by counting the number of sides and adding the number of corners. But finding the perimeter of polygons brings another element into the geometric picture.

This hands-on sidewalk chalk activity gives your child practice finding the perimeter of polygons, while teaching him how to describe geometric figures using mathematical terms. It’s a fun way to bring out his creativity and strengthen his visual thinking!

What You Need:

• Chalk
• Sidewalk or driveway
• Ruler
• Pencil
• Paper

What You Do:
Step 1
Ask your child to describe a polygon in his own words. If he isn’t sure what the term means, remind him that a polygon is a closed figure with straight sides. Ask him to draw one on the sidewalk.

Step 2
Now have him draw a group of four polygons. Suggest that he draw the biggest and the smallest polygons that he can. Ask him to draw a polygon with many sides. Then have him draw a polygon with the fewest number of sides possible.

Step 3
Take the ruler and help your child measure each side of each polygon to find the perimeter of each figure. Remind your child that the perimeter is the measurement around a figure. Measure each side to the nearest half inch, and record the measurements on a piece of paper.

Step 4
To find the perimeter of each polygon, add up the measurements of each side.

Step 5
Which polygon had the greatest perimeter and which polygon had the smallest perimeter? Have him count the number of sides and the numbers of corners of each of the polygons.

To reinforce this activity, take time to point out the polygons you see in everyday life, such as eight sided stop signs, four sided squares, and five sided honeycombs. You’ll be heightening his geometric awareness, and tying math concepts to the real world!