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Q: Answer this riddle for two dollars ( Answered 5 out of 5 stars,   2 Comments )
Subject: Answer this riddle for two dollars
Category: Miscellaneous
Asked by: sevennus-ga
List Price: $2.00
Posted: 09 May 2004 01:22 PDT
Expires: 08 Jun 2004 01:22 PDT
Question ID: 343446
You are in a conrete room.  There is a steel pipe 25 centimeters in
length cemented into the center of the concrete floor.  The pipe
portrudes about 15 centimeters out of the ground.  A ping pong ball is
dropped down the pipe.  There is about a quarter of a centimeter
clearance around the ping-pong ball and the pipe.  Your task is to get
the ping pong ball out of the steel pipe undamaged.  The only items
that are available are a wooden ruler, a ball of string, a pocket
mirror, a paper clip, and a small magnet.  Since nothing else is
allowed into the room, how could you get the plastic ping-pong ball
out of the pipe?
Subject: Re: Answer this riddle for two dollars
Answered By: till-ga on 09 May 2004 02:08 PDT
Rated:5 out of 5 stars
The answer is:
"Pee in the hole."

"Ping Pong in a Tube 
Teaser ID #2158  Fun  (2.97) Difficulty  (2.17)  Category Science 
Submitted By RayneeDay 

You are in a room that is an 8x8x8 perfect cube. There are no windows,
or doors (don't ask me how you got in there!) In the center of the
floor there is a 12 inch pipe that is sticking 6 inches out of the
floor. In the bottom of the pipe is a ping pong ball with a diameter
that is one millimeter smaller than the inner diameter of the pipe.
You have a 12 inch piece of string, a match, a magnifying glass, a 6"
ruler and a paper clip. How do you get the ping pong ball out of the
( )


Search strategy:
( ://
sevennus-ga rated this answer:5 out of 5 stars
you got it!

Subject: Re: Answer this riddle for two dollars
From: snesprogrammer-ga on 09 May 2004 08:32 PDT
I don't believe that.
25 cm x ping pong ball size = a lot of pee.
Good luck doing that.

I would bend the paper clip into a semi-circle and tie the string on both sides.
Lower it into the hole and when it hits the top of the ping-pong ball
it will fall to a side.  Regardless of which side it falls to it will
be "parallel" with the pipe wall and fall down the edge to the bottom.
 Pull gently, at an angle away from the side the clip fell on (if you
can't see down there, shine light down with the mirror) ... it should
lift the ball slightly as well as move the clip slightly under.  Do a
few short snaps until the ball bounces/rolls on top of the semi-circle
paper clip (it should rest between the groves of the wires).  Gently
pull ball to safety.

Sure it takes patience.  But it's better than waiting a few days
hoping you'll piss fast enough to fill the pipe since you need so much
volume and you're racing against evaporation.
Subject: Re: Answer this riddle for two dollars
From: carnegie-ga on 09 May 2004 09:57 PDT
Dear Sevennus,

Would you have enough urine available?  An interesting question!

According to

the regulation table-tennis ball is 38 or 40 mm in diameter.  With a
quarter-centimetre clearance all around, that makes a pipe of around
45 mm diameter.  The volume of 25 cm of this pipe (pi-r-squared-h) is
almost 400 ml.


we see that the typical adult human bladder can contain 600 to 800 ml,
but that the "micturition point" (at which there is an urge to
evacuate the bladder) is between 150 and 300 ml.  So you would
probably have empty a full-feeling bladder twice to achieve the

I trust this helps.


Search terms: table-tennis ball size mm; human bladder capacity

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