(pi) is equal to 3.14159265.... . Pi is equal to the circumference of the circle divided by its diameter, (which is taken from the formula for the circumference of the circle which is
where r is the radius and d is the diameter.) People have been looking for fractions which are equal to
and the usual fraction used is 22/7. These are only the common used values for pi but there are many other series, fractions and such that are made famous by mathematicians.