Every year math enthusiasts everywhere celebrate pi, a celebrity among mathematical constants, on March 14 (3/14), also known as Pi Day. Extreme enthusiasts have a special celebration at 1:59 (aka, Pi Minute).

Pi is the symbol for the ratio of the
circumference of a circle to its diameter. Whatever the size of a
circle, if you divide its circumference by its diameter you will always
get 3.14159..., better known as pi.

Pi is an irrational number, continuing
infinitely without repeating. It is usually estimated to the hundredths
place (3.14), but with the use of computers, pi has been calculated to
over 1 trillion digits past the decimal.

Although the ratio has been around for
about 4,000 years, the symbol just turned 300 years old in 2006. The
symbol for pi was first used in 1706 by a Welsh man, William Jones, and was made popular after Swiss mathematician Leonhard Euler adopted
its use in 1737.

### NCTM Resources

Mathematical Lens: Pi All Month

(*Mathematics Teacher*, March 2014)

Students analyze a photograph to solve mathematical questions related to the images captured in the photograph. This month, photographs of the Salvador Dali Museum in St. Petersburg, Florida, serve a generous helping of pi from the editors.

Explorations with a Paper Circle

(*Student Explorations in Mathematics*, March 2007)

Mathematical relationships can be
found and explored in many situations. In honor of Pi Day, this issue of Student Math Notes explores the circle.

Let's Take Another Look at Pi Day** – **Explores the many uses of Pi Day.

(*Mathematics Teaching in the Middle School*, March 2002)

Playing around with "Mono-pi-ly"

(*Mathematics Teaching in the Middle School*, February 2006)

The game of "mono-pi-ly" for two to five players was created as a part of a Pi Day activity for use with a mixed-level geometry class. Students review and practice circle vocabulary, and area and circumference calculations by playing the game. Playing time is approximately 40–50 minutes.

Illuminations Lessons and Activities

Investigate Pi and Archimedes' method of approximating Pi.

### Other Resources

Pi Day. Accept the Challenge. The Pi Day Challenge is a series of puzzles that are logic based. A team of logicians adapted or created these puzzles – some require research, some require mathematics, some require pure savvy.

Joy of Pi contains a wide range of links to pi pages on the Web including those on memorizing pi, posters to print, pi mysteries, fun with pi, wacky pi stuff, and a pi fan club.

Teach Pi bills itself as "a one-stop Pi Day shop for teachers and number lovers." Includes stories, more than 50 pi-related activities, and music.

### Just for Fun

Happy Pi Day! Here’s Some of the Wackiest Celebrations around the World

This article in *TIME* lists some crazy Pi Day celebrations.

Pi Day Pinterest Board

A collection of images from NCTM Illuminations to help you celebrate.

10 Pies for Pi Day

The traditional way to celebrate is to eat a pie. Or bake one. Here are some wonderful Pi Day pies to try.

How to Calculate Pi by Throwing Frozen Hot Dogs

The *New York Times *science writer John Tierney wrote a March 2008 Pi Day article which includes a link to an applet that calculates pi by using Buffon's Needle, and introduces "pi-ku" using a 3-1-4 syllable pattern rather than the traditional 5-7-5 syllable pattern of haiku.