# Holidays

## Pi Day

**What does Pi Day celebrate?**

Pi Day celebrates the number pi, also written with the Greek letter π.

**When is Pi Day celebrated?**

March 14th. This is because the number π starts out with 3.14 and March 14th can be written 3-14.

**Who celebrates this day?**

This is just a fun day to celebrate math. It's mostly celebrated by mathematicians, math teachers, rock stars (just kidding), and math students.

**What do people do to celebrate?**

People do all sorts of crazy stuff to celebrate. They learn how to calculate the circumference of a circle. They memorize Pi to the 100th digit. They have math contests and see who can do their multiplications the fastest.

Some people may actually do fun stuff like having a pie eating contest with real pies such as apple or chocolate pies. Mmmmmm!

**Fun Activities for Pi Day**

- Have the students bring circular objects from home and then figure the circumference of each by measuring the diameter.
- Hand out cookies and require each student to figure out the circumference of the cookie before they get to eat it.
- Students donate money for a charity. The class who donates the most money gets to "Pie" their teacher (be sure to wear safety glasses and have an adult do the "pieing").
- Hold a math Olympics on this day. Have a math bee as well as pi memorization contests. Throw in a pie eating contest for extra fun!
- Make a paper chain where each link has the next number of Pi on it. See how long you can make it.

**Why is Pi important?**

Pi is defined as the ratio of a circle's circumference to its diameter. The circumference is the distance around a circle and the diameter is the distance across a circle. By using Pi you can figure out the circumference if you know the diameter using this equation:

C = π * D

Where C = circumference and D = diameter.

**History of Pi Day**

Historians believe that a number close to Pi was first used to figure the circumference of a circle around 4,000 years ago by the Babylonians. Around 200 BC the Greek mathematician Archimedes continued to work on getting a more accurate number for Pi. In the 1600s, mathematicians such as Isaac Newton used math called infinite series to get even more accurate numbers. The Greek letter π was first used as the symbol for the number by Swiss mathematician Leonhard Euler.

The first organized Pi Day was in 1988 at the San Francisco Exploratorium. Physicist Larry Shaw had the idea to celebrate the day by marching around a circle and then eating some pies. They still have the celebration today.

In 2009 the US government recognized the day as National Pi Day.

**Pi Goes on Forever**

As far as we know the number Pi goes on forever. It never repeats and never ends. In math you can use an approximation like 3.14159.

**Fun Facts About Pi Day**

- Pi approximation day is held on July 22 because Pi is the approximate value of 22/7, hence the date 7-22.
- The Massachusetts Institute of Technology (MIT) mails its acceptance letters to arrive on Pi Day.
- March 22nd is also the great scientist Albert Einstein's birthday.
- Pi is also used to calculate the volume of a cylinder.
- Once in a Star Trek episode, Spock fooled an evil computer by asking it to calculate the last digit of Pi.
- Pi is considered an irrational number because it continues on infinitely in a random sequence.
- The number 360 is at the 359th digit of Pi. There are 360 degrees in a circle.

**March Holidays**

Read Across America Day (Dr. Seuss Birthday)

Saint Patrick's Day

Pi Day

Daylight Saving Day

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