An economist, an engineer, a computer scientist, a mathematician, and a physicist have lunch together. The fun begins when it's time to pay the bill. It's an involved conversation, but here's a snippet:
Engineer: Is everyone’s money in? It seems we’re a little short…
Physicist: How short?
Engineer: Well, the total was $104, not including tip… and so far we’ve got $31.07 and an old lottery ticket.
Physicist: Close enough, right? It’s a small error term.
Mathematician: Which of you idiots wasted your money on a lottery ticket?
You can try to guess where this goes, but it goes in several directions. Read the rest, with illustrations, at Math with Bad Drawings. Link -via Metafilter
The rule of thumb at my undergrad was: "Youngest, non-math major splits the check and works out tip."
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