Just a quick Pi Day pointer for you geometry teachers: be sure to stress to students that Pi is a constant rather than a variable. The misconception that it’s a variable comes in part from the fact that we often express circumference and area in terms of Pi. I especially notice confusion when students work with the formula, Circumference = 2πr (something about multiplying the two outer factors, r and 2, and leaving π alone that gives students the impression that π is a variable).

Happy Pi Day!

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It is important to emphasize that pi is the ratio between the circumference and the diameter of a circle, any circle. I have always found it fascinating that you can take any circle’s circumference, divide by the same circle’s diameter, and get one number, which is pi.

I realize that all of you know this already but I love this truth and always share it with my students. It is an instructive exercise for students to measure the circumference and diameter of a variety of circles and find this out for themselves. (Most can use the practice measuring, as well!)

It is important to emphasize that pi is the ratio between the circumference and the diameter of a circle, any circle. I have always found it fascinating that you can take any circle’s circumference, divide by the same circle’s diameter, and get one number, which is pi.

I realize that all of you know this already but I love this truth and always share it with my students. It is an instructive exercise for students to measure the circumference and diameter of a variety of circles and find this out for themselves. (Most can use the practice measuring, as well!)