When I was growing up, September meant a change of temperature, a new school year and tickets to the obvious fall sports – soccer and football.

Now it seems there is no clear ending or beginning to any sport season. There’s spring soccer, fall baseball and summer football leagues. Kids play basketball in the spring and swim all winter long. I see a teachable moment here.

Gather together all your children’s sports’ balls. If you’re like me, you’ve got a plethora of sizes, shapes and colors. What a great opportunity to use hands-on familiar objects to reinforce skills like color, size and shape with younger children while demonstrating how easy it is to calculate circumference, diameter and radius with the older ones.

One thing I remember clearly from teaching school is that measurement is a very abstract subject for many children. If we can take everyday items like balls and use them to teach, then the experience is way more memorable. Even better if you can give your children a real life task. “We need to store these balls in the garage. Can you help me measure their circumference so we can see which ones go where?” The first question you’ll get is, “What’s a circumference?” Now you’re on your way to the teachable moment!

Here’s a quick refresher course on middle-school math:

Circumference: The distance around a closed curve

Diameter: The distance across the middle of a circle

Radius: The radius is ½ the diameter and is an important number for future math equations

Here’s an easy way to start. Take an 18” piece of string or yarn and lay it on the table. Have your child make a completely closed circle with it. Then take that string and lay it out into a straight line. Use a ruler to measure its length. Place it back into a circle and ask your child to tell you the distance around that circle. Hopefully, they will say 18” because it’s the same piece of string.

Explain that the length around the outside of the circle is the circumference.

You can introduce diameter and radius in the same way. Take a smaller piece of string or yarn and run it across the middle of the circle. Measure it. That’s the diameter. Half is the radius. Have fun with it. Use a ruler, then a tape measure. Talk about why tape measures were invented (to measure things that are not straight). After you measure several balls, older children should be able to discover that the radius is half the diameter. There are all kinds of science concepts you can explore once you pique their curiosity and start experimenting.

Take a tape measure and wrap it around each of the balls. You do not need to have exact measurements. The purpose is to familiarize children with the concept of measuring things that are not in a straight line.

Tally the measurements so each child can compare and contrast the sizes of tennis balls, golf balls, basketballs, baseballs, bowling balls and ping pong balls. Footballs can also be included but be sure to point out that they are a special shape called an ellipse, and different measurement techniques apply.

After you measure, you can roll the balls down a slide or other type of inclined plane. Have them predict which ball(s) will roll the fastest, slowest and why. Could it have something to do with their circumference? Size? Weight?

Remember that when you’re done, you really do need to store those balls somewhere in the garage to validate all their hard work. ?

Robin Berlinsky is the director of education at the Children’s Museum of the Lowcountry, adjunct professor at the College of Charleston, School of Education, Health, and Human Performance and is the owner of niki leigh spa parties. She has taught in the Charleston County School system and has three children. For more information, contact Robin. Berlinsky@gmail.com.