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Pi Day: Infinite ways to celebrate the magic of circles

Celebrate Pi Day with City Year AmeriCorps

Throughout history, the humble circle has ignited debate, inflamed passions and intrigued many brilliant minds. How, you may ask? Just take a closer look at a circle near you, like the lid of your coffee cup or water bottle. Now, split that circle into two even halves by running a line through its center, and compare that length to how far your finger travels when it traces the perimeter of the lid once.

Wherever you buy your brew or your water, the distance around the circular lid will be a little over three times the distance across it! Try it again, with any circle—the wheel of a car, a ring or a clock on the wall—and the answer will be ALWAYS be the same. The distance around is always a bit more than three times the distance across the middle—in fact, about 3.14 times!

This is one of the mysteries of circles that you can help your students discover next week on Pi Day, an entire day celebrating the number 3.14, which of course take place on 3/14 or March 14. You and your students will be in good company as you puzzle over this number known as pi, or py, represented by the Greek letter π.

From the ancient Chinese to engineers at NASA, who used pi to figure out how to parachute onto the planet Mars, many people have learned that pi comes in handy. In fact, pi is about as useful as it is long—that’s infinitely long.

Want to test this out? You can see for yourself by exactly measuring the distance around the edge of a circle, or its circumference, and dividing by that distance across the middle, or diameter. You can divide those numbers all day, and you won’t finish! That’s why you’ll see pi rounded to two decimal places – 3.14.

an AmeriCorps member is leaning over to point out something on a student's paper while they work on an assignment in class

To help you engage with students next week about pi and do some fun activities, check out the resources below. Whether or not your students end up pursuing a field like science, technology, engineering or math, they’ll discover that pi is a very useful number to know!

P.S. In Greek, the word for circumference is perimetro (just like in Spanish!) The first letter in perimetro is p, which in the Greek alphabet is the symbol π!

Share your Pi Day events on social media with #piday.

This is an updated version of a story published last March.

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