A mathematician, physicist, and engineer are walking through a parking lot at night when they meet an old woman standing by a Volkswagen in tears. They ask her what’s wrong, and she replies: “I was trying to get into my car to drive home, but I dropped my keys. My eyes are too old to see them in the dark… my legs are to old to bend down and search for them. What am I to do?”
The three professionals offer to help. Immediately, the engineer drops to all fours, crawling around the car in the dark, reaching and feeling for the keys. But he does not find them.
The physicist reaches into his pocket and pulls out a small magnet and cigarette lighter. He uses the lighter to dimly illuminate the area around the car; he uses the magnet to try and attract the keys to him. But he does not find the keys.
Finally, the mathematician surveys the problem. He then goes to the other end of the parking lot, where the light is better, and looks for the keys over there.