Books, sites, guides about mental arithmetic by hand and tricks? Please recommends books I can get, from amazon? I need to get really good at mental math and math by hand, because I'm taking an exam soon  without a calculator. 
 A: If you're looking for books about rapid arithmetic calculations, then these two books might be what you're looking for. They are Speed Mathematics and Short-Cut Math, which will cost you less than $15 for the both of them from Amazon. I bought them for my little sister a few years ago, since she wanted to learn some mental math tricks, and she said that they were both pretty good.
A: There is also "Secrets of Mental Math" by Arthur Benjamin.
A: One classic text is The Trachtenberg Speed System, which actually has an amazing history: Trachtenberg created the tools for the book (speed mathematics, including multiplication) while in a Nazi concentration camp, without the use of paper or a writing utensil.
The Wikipedia page gives a pretty good overview of the book, and there is a bit about Jakow Trachtenberg on Wikipedia as well.
p.s. Don't let the \$91 price on Amazon.com worry you; you can find many used copies for less than \$10.
A: The best book for mental math and math by hand is Vedic Mathematics by Bharati Krsna Tirthaji. Just search in Google and Amazon.
A: On the website http://www.math-magic.com/ you can find some tricks for mental arithmetic.
They are divided into various categories, like Multiplying numbers, Multiplying strategies, Basic memorization, etc.
