March 14 is one of my favorite days. It is one of those days that is lurking in the shadows; most people are completely unaware of the significance of this mathematically important day. March 14 is Pi Day. Pi, that constant number that describes the ratio of a circle’s circumference to its diameter. Yes, 3.14159265358979 . . . well, because pi is an infinite number, I’ll just stop there.

Or not. Because, well, I just have to make sure you understand how

**significant** March 14, 2015, really is – especially at 9:26 a.m. Significant? Did you get it? The first eight significant digits of pi are 3.1415926 – aha! 3-14-15 9:26! If you are really geeky, you can take it to the second at 9:26:53.

OK, that was really geeky. Sometimes, geeky can be a great way to introduce students to math and geometry concepts. There are some fun things you can do with students of all ages to explore circles, area, circumference, diameter, and radius on Pi Day.

An art teacher once told me it was humanly impossible to draw a perfect circle. I’m sure that’s because he didn’t have a

Circle Perfect Compass or a

Metric/Decimal Circle Template. I can draw great circles now! A simple compass or template can make circle drawing much easier, and more practical, for some Pi Day fun.

Challenge your students to draw circles of many different sizes. Encourage them to make really, really big circles and really small circles (that are still measurable). If drawing isn’t your forte, simply provide students with circular objects. Then, have them measure and record the diameter and circumference of each circle. A piece of string might help with the circumference measurement. Finally, have students divide the circumference by the diameter of each circle. Sit back and watch as they are amazed to see 3.14 appear for each circle, regardless of the size.

If it happens to be a beautiful spring Pi Day, consider using the outdoors to help get the point across (

*across* as in diameter). Have students predict the circumference of a tree and then use a string to actually measure it. I bet the predictions are smaller than reality. Finally, have students calculate the diameter of the tree using the pi formula.

If you want more ideas, simply do an Internet search for “pi day.” I guarantee there will be more than 3.141592653 hits. The

Pi Day website is especially fun and includes a page of activities submitted by teachers and students. The site also includes videos that celebrate my favorite irrational number.

Personally, I think we should eat pie on Pi Day. Even though the formula for area tells us pi are square (A = πr²), we all know pies are round – and tasty! Happy Pi Day!

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