# Pi

| **Pi** (the symbol is the Greek letter π) is:
*The ratio of the ***Circumference** to the **Diameter** of a Circle.
| |

In other words, if you measure the circumference, and then divide by the diameter of the circle you get the number π It is approximately equal to: **3.14159265358979323846…**
The digits go on and on with no pattern. In fact, pi has been calculated to over one million decimal places and still there is no pattern. |

## Approximation

A quick and easy approximation to Pi is 22/7

22/7 = **3.1428571...**

But as you can see, 22/7 is **not exactly right**. In fact Pi is not equal to the ratio of any two numbers, which makes it an irrational number.