This is not a student idea but I thought that this was real cool and would interest other math-magicians! ;)

Nice!

Along those lines, for those who like to do sudoku in class- besides 453…

http://www.kidsnumbers.com/math_magic.php

it's more of a sudoku meets math game.

oh Alli, you know how I need my daily soduku…..this is awesome!! thanks!!

http://www.ted.com/index.php/talks/arthur_benjamin_does_mathemagic.html

Whoops, forgot to post the clip.

Alex, this is so perfect for you. I could just imagine you doing this on your first day of class as a teacher. This is really amazing though how he can calculate so fast. I still have to use my fingers for the trick when multiplying by 9s. I have no idea how he could figure this out except for memerizing certain tricks with the numbers that he is given. I'm sure there are millions of tricks and stuff out there for how to do this, but here is one that I found that was really clever. I still don't think that I could do it as quick as he can!

http://wildaboutmath.com/2007/11/04/how-to-square-large-numbers-quickly-part-1/

That's quite a way to square numbers (from the article in the last post). However, I'm not surprised that we didn't learn tricks like that in secondary school since it would be very time consuming. Along that note though, it would be great to have an outside resource containing information and tricks like this for students who would want to learn more about numbers. Like it said at the end of the last article, once you can do that trick efficiently, you'll enjoy math much more.

I recently bought a book at the Union Book store, and its exatly the resource you are talking about. It's called **how to calculate quickly: Full course in speed arithmetic** By Henry Sticker. It gives different techniques and tricks to do fast multiplication, division, addition and subtraction. Now I just have to read it :)

Awesome, I'll have to go find that!