I'm a math major in school. I'll be applying to graduate school for math in a few months. I'm taking the General GRE in a couple weeks and the Math Subject GRE not long after. So, to help me prepare I bought a few books on... arithmetic?
Yes. See, I have a problem. I screw up arithmetic constantly. I have actually written the following on a Calculus test: "6 + 3 = 8." Usually I'm not quite that bad, but when adding/multiplying large numbers, chances are extremely high I will make a mistake.
So I thought maybe there were other algorithms out there that could improve my accuracy here, and I ordered some books. Unfortunately, I don't believe this system is helpful. It mostly consists of reworkings of the standard multiplication/division algorithms. They are described in such a way that it may not be immediately apparent that that's what they are. For instance, instead of memorizing, say, the times table for 6, you memorize a rule for how to multiply a digit by 6. This really doesn't buy you anything.
The methods usually involve less writing down intermediate steps, but all the same calculations are there.
One very good thing mentioned in this book is the error checking method "casting out nines," here called the "digit sum method." However, this is not original to the system; it has been around for hundreds of years (as the book admits). Plus, unfortunately, the book does not make clear that it is possible for a calculation to pass this error check and still be incorrect; that is, when the check says you're wrong, you're wrong, but when it says you're right, you're only *probably* right. In fact, the book strongly implies the contrary.
The foreword claims that students using this system faced off in a test of arithmetic against "mechanical brains" (did people really call computers that??) and the students won. Hmm. Well, the mechanical brain sitting on my desk right now can do millions of arithmetic operations per second. This kind of statement may have *almost* made sense in 1960, but today...
Lastly, I have to complain about one more thing. This book strongly encourages a misconception that some people have about mathematics. I'm referring to the idea that arithmetic IS mathematics, and that being good at mathematics means being good at arithmetic. Arithmetic is to mathematics as spelling is to poetry.