While enjoying the entertainment of Marc Salem's "Mind Games" show on
broadway, one thing piqued my curiousity more than others.  At one
point during the night, he makes a 3 by 3 box grid on a notepad & has
the audience RANDOMLY put one whole number - between 1 and 9  in each
of the 9 boxes.  This is done by a true participant from the audience.
 The participant than brings the notepad with the 9 random #'s in the
9 boxes up on stage to yet another audience participant who adds the
#'s column by column or row by row to get the answer. (in other words
if the 3 boxes in row 1 had the #'s 5, 6, & 9 - This would be counted
as 569 + the next 2 rows or columns) The answer he
gets is 1576 - he writes it down on a big piece of paper & than has a
boy put a cassette tape he had been holding on to during this process
into a tape player & it has his voice telling the audience "tonight's
answer is going to be 1576".  The crowd went crazy.  I'm almost sure
that I know how this is done but I was willing to spend a few dollars
to see what you all thought.  Question:  Is there some law of averages
or mathematical answer to this 'stunt'?  If so, what is it?  If not,
how do you suppose he got the answer to be what he had on his
recording?  Do you think he just fooled us all by switching the
notepad to have pre-written #'s?  Like a regular "magician" would be
able to do?  Thank you.