I was at an IBM meeting about 8 or 9 years ago when I saw a most interesting performance, from memory is utilized 100 pennies arranged in a square outline. The magician had four people sit on each side of the table and one by one he asked each of them to count how many pennies they had on their side of the square. He then asked each one by one to choose a penny to be removed from their side. As they spectator did so, the magician removed the penny and then rearranged that side of the square that the penny was taken from and asked the spectator to count how many pennies were they had making up their side. Due to the way the pennies were rearranged the spectators number never decreased. This was done for each of the spectators several times, and each time they counted how many they had, their number of pennies never decreased.

Can any one tell me the name of this mathematical trick and where I might source a book on it? When I asked at a recent meeting, no one recalled the trick I was referring to.

Many thanks.

You need to get a copy of Steinmeyer's impuzzebilities (the first booklet)
he has a very nice routine in there called the bermuda triangle which is essentially the same.
I do not know the source of this very very old trick.

unfortunately if you are just a bit mathematically inclined this trick doesn't even puzzle. I saw a very good magician which performed this trick flawlessly and beautifully to a group with 2 engineers present.
they were going "yeah of course... why should I be amazed from this"

ND

If you can find Michael Weber's book "Lifesavers", he also has a great routine in there. It's called "To Feed Many". It's the same principle as "Bermuda Triangle".

It had been used by magicians from India since ancient times. However, it wasn't popularized in the U.S. until Doug Henning brought it over from India!

As far as being mystifying, you need to present the routine properly. If you need some inspiration, check out my Memorable Magic posts (with more to come!).

Thanks very much for the suggestions. I look forward to checking them out

Bob Longe's book "Money Magic Tricks," published by Sterling Publishing Co. and probably out of print :-( , has a trick called "The Great Escape." I can't exactly understand Longe's directions for this one, but it is another example of this kind of trick.