In a high school gym class, all the girls are lined up against one wall, and all the boys against the opposite wall.

Every ten seconds, they walk toward each other exactly half the remaining distance between them.

A mathematician, a physicist, and an engineer are asked, "When will the girls and boys meet?"

Mathematician: "Never."

Physicist: "In an infinite amount of time."

Engineer: "Well... in about two minutes, they'll be close enough for all practical purposes."