Question

we know that area of circle is pi r square ,but who knows what is pi?

Answer 1

Pi is an irrational number.
The value of pi or π is 22/7 or 3.14.....
An irrational number is one which doesn't end.
when you divide 22 by 7 and when you will reach to the decimal point , you will find that the value after the point never ends.It will continue till infinity.

Circle being a curved shape, it was difficult to depend upon a certain dimension. It was observed that the circles' area and circumference depends upon its diameter.

Initially, the circles' circumference was measured roughly using threads. The ratio of the circumference and the diameter, i.e. (Circumference/Diameter) among the circles was observed to be similar but not equal.

Aryabhatta defined the irregularity of this ratio to be an Irrational Number. He also found the value of this ratio upto 5 significant figures as 3.1416.

This ratio is what is called as π (pi).

Answer 2

pi is circumference /diameter of any circle