## What is Pi?

Pi is the ratio of a circle’s circumference to its diameter. No matter what is the size of the circle, pi is always the same number. For any circle, dividing its circumference by its diameter will give you the exact same number: 3.14159…or pi.

## Discovery of Pi

It is said that Pi has been known for nearly 4,000 years and was discovered by ancient Babylonians. The Great Pyramid at Giza, which was built between 2550 and 2500 BC, has a perimeter of 1760 cubits and a height of 280 cubits, which gives it a ratio of 1760/280, or approximately 2 times pi.

The earliest textual evidence of pi dates back to 1900 BC; both the Babylonians and the Egyptians had a rough idea of the value. The Babylonians estimated pi to be about 25/8 (3.125), while the Egyptians estimated it to be about 256/81 (roughly 3.16).

## How did Archimedes discover it?

Archimedes was one of the first mathematicians to discover the approach to estimate a Pi. He figured out how to estimate the perimeters for polygons with twice as many sides. He went from a 6-sided polygon, to a 12-sided polygon, to a 24-sided polygon, to a 48-sided polygon, and ended up with a 96-sided polygon. This final estimate gave a range for π between 3.1408 and 3.1428, which is accurate to two places.