Res Botanica

Originally: Buffalo Museum of Science
1020 Humboldt Parkway
Buffalo, NY 14214
September 20, 2001
Return to Home


This is a class of problems called "np hard." No, no, don't quit . . . the math is hard, the puzzle below is way easier. (I think.)

Np ("non-deterministic polynomial") hard problems are those that get harder as you try to solve them. Every attempt at a solution produces even more problems. There are lots of Web sites on "np hard" or "np complete" math, and you can examine those if you think they will help with the puzzle (heh, heh, they won't).

According to William Poundstone (1988 - Labyrinths of Reason, Anchor Press, NY) a labyrinth is a kind of np hard problem. In any maze (or even a terrorist network), you have to actually go to the end of a passage to check it out. There is no quick way to get through a labyrinth (though there are lots of optimization procedures on how to best get through with the least effort).

But sometimes a mechanical model of a problem can be solved with some ingenuity.


Somebody builds a maze with a tight-fitting lid. You can't see how the maze twists and turns. There is an opening to start and an opening to come out. Your job is to send a ping pong ball through the maze without the ping pong ball going down any dead-end passage.

You have a whole machine shop and a basement full of household tools to help, but you can't open the maze or x-ray it or otherwise figure out the path first. You must send the ball through on the first try, exactly down the correct path.

Question: How do you send the ball through the covered maze without it going down a dead-end path? ALSO Why does your method work?


You have to get the answer right AND explain why your answer is right. Take your time.

For the answer, click here.