What Is Pi (π)?
Pi (3.14) is a ratio. A ratio is a statement of how two numbers compare. Pi is the ratio of the circumference of a circle compared to its diameter. It is found by dividing the circumference of a circle, or distance around a circle, to its diameter, or distance across a circle through it’s center. Pi = C/d.
Pi is always the same number no matter the size of the circle. The symbol for Pi is π and is pronounced “pie”.
Why isn’t Pi rational?
Pi is an irrational number, which means that it is a real number with decimal that repeats forever. There is no exact value for the number since it repeats infinitely.
If you would like to investigate π on your own, try this brief experiment from Scientific American.
- Using a compass, draw a circle.
- Take one piece of string and place it on top of the circle, exactly once around.
- Straighten out the string; its length is called the circumference of the circle.
- Measure the circumference with a ruler.
- Measure the diameter of the circle, which is the length from any point on the circle straight through its center to another point on the opposite side. (The diameter is twice the radius, the length from any point on the circle to its center.)
- If you divide the circumference of the circle by the diameter, you will get approximately 3.14–no matter what size circle you drew!
- Now, retest larger circles.
- A larger circle will have a larger circumference and a larger radius, but the ratio will always be the same. If you could measure and divide perfectly, you would get 3.141592653589793238…, or pi.
Visual representations of Pi via Wikipedia.