# What is pi?

## Definition of Pi

Pi (Π) is the ratio of the circumference to diameter of a circle. Try measuring round objects like jar lids and see the ratio of their circumference to their diameters.

### A story about a number called Π (Pi)

Say you walk about the edge of a circle and you know just the diameter (line joining the two ends of the circle); but you wish to find out how much exactly you walked. You calculate the distance (circumference) by multiplying π x diameter. You also find the area of the circle= Π r²

## Value of Pi

- Pi from Greek letter π has a value of 3.14159…this term was adopted by Leonard Euler.
- This number is always the same and will never change no matter what the diameter or circumference of a circle is.
- Pi is an infinite decimal as it is a decimal number that has numbers repeating after it constantly. Thus we put “..” after writing the first few digits after the decimal point.
- Pi does not have a pattern of its infinite numbers and this has been checked till the quadrillionth place.
- Pi is an irrational number as we can never stop writing the numbers following the decimal point.

## History of Pi

4000 years ago, the Babylonians measured the area of a circle by 3x the square of its radius. Π=3

### How does Pi (Π) relate to our lives?

- “May I have a large container of butter today”- 3.14159265 is an easy way to remember the first few digits of pi.
- Pi Day celebrations are on 14th March (3rd month). It is also Albert Einstein’s birthday.
- Kellalur Nilakantha Somayaji was the Indian mathematician who formulated the Nilakantha series for calculating pi- 3 + 4 /2×3×4 − 4 /4×5×6 + 4/ 6×7×8 − 4 /8×9×10 + …
- The Great Pyramid of Giza has a ratio of 1760(perimeter)/280 (height) ≈ 6.2857 or 2π ≈ 6.2832.

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