Tomorrow (March 14) we celebrate Pi Day! Pi is the name of the number that is found when the circumference of a circle is divided by the diameter. It doesn’t matter how big or how small the circle, the answer will always be pi! The number pi begins with 3.14, which is why in America we celebrate Pi Day on March 14 — 3.14. Since pi is such an important number in mathematics, it has its own special symbol, the Greek letter, 𝛑. Pi is an irrational number, meaning that as a decimal it goes on forever without repeating. A fun mind blowing fact to share with your students is that because the decimals in pi go on for forever without repeating, every personal number they know (their birthday, their phone number, their social security number) will show up somewhere in pi!

Keep reading to see how we calculate pi using a pizza pie!

#### Help your students recognize the value of pi by calculating pi themselves for a variety of circular objects!!

#### Materials

Various circular objects such as a tape roll, cup, plate, bowl, quarter, etc

String

Meter stick or measuring tape.

#### Directions

Use the string to wrap around the circumference of an object.

Stretch out the string and use the meter stick to measure it.

Use the meter stick to measure the diameter of the object.

Divide the circumference by the diameter.

The answer will always be (approximately) pi!

Check out the pictures below of the activity done with a pi-peroni pizza pie!!

First we used a string to measure the circumference of the pizza and measured the length using a measuring tape. Then we used a string to measure the diameter of the pizza. Can you guess how accurate our measurements and calculations were???

In these photos you can see (if you zoom in) that the circumference of our pizza is 88cm and the diameter of our pizza is 28cm. Lets see how close we get to pi....

We calculated pi EXACTLY! Math is beautiful in it's predictability and repeatability. How close can your students get??

## Check out even more Pi Day resources!

National Pi Day Website: A whole website devoted to Pi Day!

“What is Pi Day?” Reading: Article from Al Jazeera about Pi Day. The article also includes a number of fun infographics.

“Pi Day Activities” List: A multitude of activities to do with students to celebrate pi!

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