Tricks for Solving Math ProblemsDate: 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 |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994-2013 The Math Forum
http://mathforum.org/dr.math/