Happy soon-to-be Pi Day! I’ve gathered some fun ideas for you to consider using with your students as part of your Pi Day celebration. Because who doesn’t celebrate Pi Day, right? But first, let’s take a look at its origins.

## When Was Pi Day First Celebrated?

Larry Shaw, a physicist at **San Francisco Exploratorium**, gets credit for having the earliest known official Pi Day celebration. In 1988, at a brainstorming retreat with co-workers, Larry had the initial idea for Pi Day. March 14, Larry and his wife served pies and tea on the museum floor to celebrate, and Pi Day has evolved since. On March 9, 2009, the **U.S. House of Representatives** recognized March 14 as National Pi Day. Additionally, in November 2019, the United Nations Educational, Scientific, and Cultural Organization’s General Conference designated Pi Day as the **International Day of Mathematics**.

## What Is Pi?

Pi (π) has been around for about 4,000 years. In Euclidean geometry, pi is the circumference (C) of any circle divided by the diameter (d) of the circle, thus giving us the formula π=C/d. Regardless of the circle’s size, the ratio is always pi. And because pi is an irrational number, it has no ending, meaning that it continues forever without repeating.

### History of Pi Calculations

Babylonians gave a rough calculation of pi as 3.125. The Rhind Papyrus from Egypt identified the calculation to be 3.1605. Next in line, Archimedes determined that it is between 3 1/7 and 3 10/71. In 1610, it was calculated out to 35 digits, and later in 1789, it was calculated with an accuracy of 140 digits– with all calculations completed by hand. In 1949, the infamous ENIAC (Electronic Numeric Integrator and Computer) calculated it to 2,037 decimals. And as of last year, it was calculated to 62.8 trillion decimal places.

## Fun Pi Day Activities

### Memory Challenge

Because pi is an irrational number, it has no ending. Challenge your students to see who can memorize the most consecutive digits and recite them by memory. Depending on your grade level, set a goal for the students to reach. Direct your students to **One Million Digits of Pi** as a reference. You can also refer to the YouTube video below to learn a song to help with memorizing 100 digits.

### A Cut Above

Students can complete this activity on their own or with a partner. All you’ll need are some paper plates, string, and scissors.

**Step 1:**Measure the string around the edge of the paper plate. Cut it to the size of the circumference.**Step 2:**Take the string, measure it across the diameter of the plate, and cut it to length.**Step 3:**Check how many diameter-length strings make up the length of the circumference string. Each group should get a little over three diameter lengths (approximately 3/20th of the diameter).**Step 4:**Redo the experiment, but allow students to use a compass and draw a circle of any size.**Step 5:**Guess how many diameter stings will match the length of the circumference string for this new circle. Usually, students will guess more for larger circles and less for smaller circles.**Step 6:**Follow steps one through three using the circle they drew with their compass. How many diameter strings make up the length of the circumference this time? (HINT: They will all get three).

Once they discover they all have similar outcomes (a little over three diameter-length strings), explain that they have discovered the constant pi. Regardless of the size of the circle, the circumference will always equal a little more than three times the diameter. NOTE: It is best to use string and not yarn since yarn is stretchy, but students will still have an “Aha!” moment if yarn is all you’ve got.

### Write a Pi-Ku

What could make a haiku even more interesting? Writing one about pi. A haiku is a Japanese poem with 17 total syllables– five in the first line, seven in the second line, and five in the third line. To give students some fodder to write about, consider reading one of the following:

### Enjoy a YouTube Video

Watch one of the videos below about pi…while eating pie.

### Paper Chain Pi

Students can create a paper chain with each link having a digit clearly written on it. Start by having students cut construction paper (or colored copy paper) into strips. Using a marker, a single digit is written on both sides of the strip. When students start assembling their pi chain, have them start with a link with the numeral 3 on it. Attach a link with a decimal on it. Then, continue adding links with the numbers accordingly. Students can tape, glue, or staple the paper to itself as they form each link.

Hang the pi chains in the hallway or an area where they can see and practice reciting the number as they go to various parts of the building. To help with memorization, make each numeral its own color. For example, all the ones are blue, twos are red, threes are green, etc. Have students make wristbands using this same strategy but with smaller paper strips.

### Pi-scrapers

Create a scene of skyscrapers using the digits of pi. Students can use a spreadsheet to fill in the cells or create each skyscraper by gluing the specific number of squares going up. If the students are making their pi-scrapers with paper, have them draw windows every so often with something happening in the building. Each window could represent part of a story the students are reading or illustrate a particular mathematical symbol.

### Math Fair

As mentioned above, UNESCO recognizes March 14 as International Day of Mathematics. So, why not hold a math fair? Similar to a science fair, a math fair highlights the importance of mathematics and allows students to demonstrate their favorite or interesting findings with math. This could be a great addition to parent-teacher conference night, where each class sets up a table outside their classroom with a math puzzle or information for the parent and other students to explore and read about. To get you started, here are a few math fair resources to check out if you have not hosted a math fair before.

## Non-Math Activities

Even if you aren’t a math teacher, you can still participate. ELAR teachers can read and write stories about famous mathematicians. Social studies teachers can highlight **mathematical geography** or explore places of influence where different mathematicians lived. Art teachers can explore mathematics through the **golden ratio**, symmetry, or **fractality**. You can also highlight artists who were also great mathematical thinkers, such as **Luca Pacioli**, **Leonardo Da Vinci**, **Albrecht Dürer**, and **M. C. Escher**.

## How Will You Celebrate Pi Day?

So, how will you celebrate? Do you have a lesson that you’ll be using? Share it with us in the comments to help other teachers. Will you be doing a particular STEM or STEAM project? If so, we’d love to hear about it.