Puzzle : calculate value of $\pi$ given area of circle

Question

I have seen in many interview experiences, interviewer asks find the value of [Pi] given area of the circle. What the interviewer is looking for and what is the answer for this?

Answer 1

The area of circle of radius $\;r\;$ is given by the formula $\;\pi r^2\;$ ,so if we know this value is, for example $\;S\;$, then

$$\pi r^2=S\implies \pi=\frac S{r^2}$$

and you get the value of $\;\pi\;$ (up to certain accuracy, of course).