When the length
of the circumference of a circle is divided by the length of its
diameter, the result is always the same number. This number is slightly
more than 3.
Pi is an irrational number, which means that it cannot be
expressed as a fraction m/n, where m and n are integers. Consequently
its decimal representation never ends or repeats. Beyond being
irrational, it is a transcendental number.
An electronic calculator
gives π as 3.1415927. This is not exact, but accurate enough for
most practical purposes. Pi is an irrational number so it cannot
be expressed exactly as a friction. 22/7 is often used as a approximation
to π, but 355/113 proposed by the ancient Chinese astronomer Ch’ung-
Chi much better. π occurs in all the formulas for measuring the
areas and volumes of circular objects such as the circle, sphere,
cylinder and cone.