Sherlock Holmes and Dr.
Watson are taking a trip across a desert by
hot-air balloon. There are not many landmarks;
so eventually, they become lost. Luckily, while
flying quite low, they see a man.
Holmes shouts, "Sir, could you please tell me
where we are?"
The man looks up, ponders for a moment, and then
answers, "Gentlemen, you are in a hot-air
At this moment, a burst of wind picks up the
balloon and carries it away.
Holmes turns to Watson and asks: "My friend, do
you know who that man is?"
"No, Holmes, of course not!"
"He's a mathematician!"
"Holmes, that's incredible! But *how* do you
"It's very simple, Watson. First of all, the man
thought before giving us an answer. Secondly,
his answer was absolutely correct. And thirdly,
the answer he gave us was of no practical use,