Pi is a mathematical term used in many formulas. The decimal form for pi, when used in determining the circumference of circles, equals approximately 3.14, but pi is part of the irrational number group and the calculation results in a never-ending string of numbers that some mathematicians claim includes every possible number combination. High school Pi Day celebrations ask students to complete projects that encourage an interest in mathematics and science. The annual nod to pi takes place in March, the third month of the year, on the 14th day -- 3.14.

## Pi of Pie

Projects involving food, and pies for special Pi Day projects, have high interest for many high school students. This project asks secondary students to make pies and then guess the ratio for each pie. Pi fans know that the ratio of each circle is a constant of approximately 3.141592653589793238 ..., but making a show by formally measuring all of the pie pans confirms this fact. Ask students to use a string and the formula for determining the circumference of any circle ((2)(Pi)(r)) to demonstrate the process for the project participants. Serve pieces of the pies to everyone involved in the project.

## Puzzle Making

Pi turns up in circle formulas when calculating the circumference, diameter, radius and area. It also appears when calculating the sum of the infinite series. Pi Day projects for high school students frequently focus on puzzles and puzzle making. Modern computers have helped identify pi's first eight quadrillion places right of the decimal, but the remaining numbers in the chain remain an unsolved puzzle. Charles Dodgson, author of "Alice in Wonderland" and a noted puzzle maker, wrote about the use of pi in 1865. Possible high school projects ask students, dressed as Alice, Lewis Carroll or one of the characters from Wonderland, to complete puzzles during the school day to reinforce the importance of mathematics.

## Personality Celebration

Historians and mathematicians have yet to know who discovered pi, but special celebrations for the day involve promoting people associated with the concept, including Albert Einstein who was born March 14, 1879. Math scholar Waclaw Siepinski, another potential candidate for Pi Day honors, was also born March 14. Other noted pi enthusiasts include mathematician William Jones who in 1706 first used the Greek letter pi as a shortcut to represent the ratio of circumference to diameter. More famous pi proponents include Archimedes, Leonhard Euler, James Gregory, John Machin and George Buffon. Possible projects for Pi Day include T-shirt or poster making of the images of famous pi promoters, recreating personal diaries or portraits for the men or developing a game format to quiz students on their knowledge of the personalities associated with the concept of pi.

## Demonstrations

One interesting fact about pi deals with the calculation consistency regardless of the size of the circle. The ancient Babylonians and Egyptians knew the importance of pi, but not all secondary students understand. Allow math students to visit non-math classes to draw two chalk circles of different sizes on the classroom board or outside sidewalk. This project then asks the class observers to guess the ratio of the circle. The math volunteer then uses a string and the formula for determining the circumference to demonstrate the answer for the classroom of students. Students can take this knowledge as a school project to the elementary schools to instruct young math and geometry fans about pi and the important concept.

#### References

- Princeton University: Pi Day
- University of Minnesota Geometry Center: 100,000 Digits of Pi
- Scientific American; What is Pi, and How Did It Originate?
- The New Method of Evaluation as Applied to Pi: Lewis Carroll
- Scholastic Teachers: Exploring Pi
- Bryn Mawr College: The Magic Sierpinski Triangle
- Ed Karrels: Computing Digits of Pi with CUDA

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