Recently I read a joke from a book named It must be Beautiful: Great Equation of Modern Science (Farmelo, 2002).

The author wrote a joke:

A mathematician, a physicist, an engineer and a biologist are together and someone asks them what is the value of \pi .

The mathematician responds crisply that it is “equal to the circumference of a circle divided by its diameters”.

The physicist counters that is is “3.141593, give or take 0.000001”

The engineer says it is “about 3”.

And, the biologist asks back, “What is \pi ?”

Someone was not happy with this joke and asked me what is the value of \pi .
I said, “I am just a tutor. Please ask your lecturer.”