March 14 is known as Pi Day and it’s also the birthday of Albert Einstein. The Exploratorium in San Francisco, California, began Pi Day celebrations over 25 years ago that have now captured the attention of math enthusiasts, globally. The celebration of Pi Day brings opportunities to have some fun with pi-related math activities and perhaps eat a piece of pie!

**The Greek letter “π”**

Pi is the mathematical constant that has been described as a “complex way to describe the simplest shape.” Pi (or “π”) is the symbol for the ratio of the circumference of a circle to its diameter, which is a never-ending number and approximated at 3.14159.

**Classroom Activities to Celebrate Pi**

**Area and Circumference of Circles Math Unit:** These math activity pages for grade 6+ help students determine the area and circumference of circles in order to answer riddles, use the concept of “pi”, and solve other problems. From Evan-Moor’s *Basic Math Skills*

**Education World Pi Day Activities:** This article shares many ideas for how teachers can celebrate pi in the classroom, such as investigations of the value of pi, special pi projects, and parties with pizza or other kinds of “pi.”

**The Exploratorium Activities and Links:** This site offers ideas for pi-related activities and recommended links. In one activity, “Seeing π,” students measure a can of tennis balls and have to determine “Which do you think is greater, the height or the circumference of the can?” The answer may not be as obvious as it appears!

**A Brief History of Pi**

- Pi has been known for almost 4000 years.
- The ancient Babylonians calculated the area of a circle by taking 3 times the square of its radius, which gave a value of pi = 3.
- The Egyptians calculated the area of a circle by a formula that gave the approximate value of 3.1605 for pi.
- The first calculation of pi was done by Archimedes of Syracuse (287–212 BC) who approximated the area of a circle by using the Pythagorean Theorem to find the areas of two regular polygons. Archimedes showed that pi is between 3 1/7 and 3 10/71.
- A similar approach was used by Zu Chongzhi (429–501), a brilliant Chinese mathematician and astronomer.
- Mathematicians began using the Greek letter π in the 1700s.
- An Eighteenth century French mathematician named Georges Buffon devised a way to calculate pi based on probability.

Source: The Exploratorium

Have a happy Pi Day!

**Theresa Wooler** has more than 10 years’ experience in K–6 classrooms as a parent volunteer and homeschool educator, has taught high school English, and is currently involved in education through Evan-Moor’s marketing communications team.