Teacher resources and professional development across the curriculum
Teacher professional development and classroom resources across the curriculum
A Common Book of Pi
The Pi Pages
The Pi Trivia Game
Pi: The Never-Ending Number
When you start playing with geometry, you eventually come across the concept of pi. When you divide the circumference of a circle (the measurement of its perimeter) by its diameter (the width across its middle), you always get the same number. That number is pi. Whether you're measuring a large circle or a small circle, the circumference divided by the diameter always equals pi. Once you know the value of pi, you can easily figure out a circle's circumference, diameter, or area. It's a very useful number in geometry.
The approximate value of pi is 3.14159, if you round it off to make it easier to use in equations. In reality, pi is an infinite number. You can't accurately express it as a fraction (like 1/3 or 5/10) and it never repeats (like 3.333333 or 2.148148148). No matter how long or how hard you look, you'll never find a pattern in the numbers. Mathematicians have calculated pi to billions of decimal places, but still have not found any pattern or repetition to the numbers.
Pi has a long history. The earliest mention of the idea was in an Egyptian papyrus dating to more than 3,500 years ago. The Egyptians understood that the ratio of a circle's circumference to its diameter was constant. They expressed pi using fractions, and figured it as (4/3)4 (about 3.16). The Babylonians had it figured as 3 + 1/8 (about 3.125).
The ancient Greeks also understood pi as a ratio between a circle's circumference and diameter. By experimenting with circles inside polygons, Archimedes, a Greek mathematician who lived in about 200 B.C., proved that pi was somewhere between 3 10/71 and 3 1/7 (or about 3.14, roughly what we know it to be today).
At last count, pi has been calculated to more than 50 billion decimal places. The power of modern computing has made calculating pi as much a competitive pastime as a serious calculation. Here is a piece of pi (forgive the pun). The number below is pi calculated to the 1,000th decimal place: