# The number π

The ratio of circumference length to its diameter does not depend on its size – i.e., is a fixed number. This number is denoted with the π letter in mathematics.

The number π can be written as an infinite non-periodic decimal number $$ \pi=3,1415926535… $$

The fact that it equals “three and change” can be demonstrated with use of a cork tea mat, rope and two pins.

Wind the rope around the mat lying on the table and cut the rope so that it had the same length as the circumference.

Sticking the pins in two diametrically opposite points, one can demonstrate that this rope would now make three folds along the diameter, leaving some “change”.

The struggle for finding the most precise value of this “change” was exciting and took centuries.

One π’s properties is that you could find your birthday date after the dot in its decimal form.