Tricks for Solving Math Problems

Date: 9/27/95 at 23:50:19
From: Anonymous
Subject: Mathematical Tricks

I recently learned a trick for multiplying 2 digit numbers by 
11. Add the 2 digits of the number and insert the sum between 
the original 2 digits. If the sum is greater than 10, add the 
digit in the tens place to the original first digit.

Ex.  23x11 ->  2+3=5  => 253
     45x11 ->  4+5=9  => 495
     87x11 ->  8+7=15 -> 8+1=9 => 957

The theory shows up quickly when you manually calculate it 
out in longhand.

My question is, do you know of any other tricks like this 
one?

I have seen TV ads for audio/video tapes promising to teach 
you tricks for multiplication, division & exponents.

Date: 10/10/95 at 21:41:58
From: Doctor Ethan
Subject: Re: Mathematical Tricks

Hey,
	The most amazing book I have ever read regarding this is
Mathemagics by Benjamin and Shermer. It is great.

Also, you can get on a mailing list that will send you a new 
math trick every week.

BEATCALC@aol.com

You'll find an archive of its tips and other math tips and tricks at

  http://mathforum.org/k12/mathtips/   

Hope this helps.

-Doctor Ethan,  The Geometry Forum