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Pi Day

Pi Day is an annual American celebration commemorating the mathematical constant Π . Pi Day is observed on March 14, since 3, 1, and 4 are the first three significant digits of Π in decimal form.

Some people are campaigning to replace Pi Day with Tau Day, June 28. Can you figure out why?

Pi is the ratio of the circumference of a circle to its diameter. While it has been calculated to trillions of digits, pi starts 3.14159. . . and in honor of this number, many people celebrate March 14 (3/14) as Pi Day. Although we are not formally observing the date this year, we have put together a few pi facts to help you think about this remarkable number.


If we wrapped a no-stretch rope snuggly around the equator of a perfect sphere the size of Earth (8,000 miles in diameter), how much longer would it have to be if we wanted to raise it 1 foot above the surface all the way around?

What about a sphere the size of the Sun (880,000 miles in diameter)? Imagine a tube made by rolling and taping a 3 X 5” file card standing on a table. Will it hold more grains of rice if we roll it the wide, hamburger way or the tall, hot dog way?

Why are man - hole covers always round?

Look at this! » This is our educators' take on Pi, but there are many ways to think of this number. Some people are even campaigning to replace Pi Day with Tau Day, June 28.