mathematician how much was two plus two.

The engineer, without hesitation, drew out his calculator, tinkered
with it for a while, and answered: four.

The physicist took out his slide rule, drew up a chart, and after a
few calculations, replied: 3.9985729 plus or minus 0.0378.

The economist smiled and responded: what would you like it to be?

The lawyer shrugged and said: if the judge isn't too conservative, I
could easily prove that it's three. That'll be $50, please.

The mathematician picked up a pencil and paper and started to deduce
it. After a few hours, he was asked for the result. His reply was: I
don't know yet, but I know that it exists and is unique...