Mental Math

When I started this blog, I promised myself that I would not write on any nerdy subjects because I figured, if you were really interested, instead of reading my hopelessly insufficient explanations, you'd wiki it. Or... maybe even go further from wiki-ing it (yes, i have turned wiki into a verb) and maybe go and get a book. But, today I might have to break that promise. I'll leave it up to... well... potentially the one person reading this blog to decide whether the post is nerdy enough, that is- academically intriguing enough to be considered nerdy.(and because I always do this: http://en.wikipedia.org/wiki/Nerd).

So I borrowed this book called Secrets of Mental Math from a good friend (at least I think we're good friends. Who really knows what goes on on the other side of things?), who, quite frankly, is a nerd. Oooooooohh! aaaaaaaaahhhhh! Anyway, I'm not much of a math, science-y person. Well, honestly, I'm not much of a humanities/artsy type either nor am I into econ, politics, whatever. I guess I just hate academics and am just too lazy to find out what I actually like. Going back to the point, I don't particularly like learning, well anything. Anything includes math. Now, let me tell you how bad I am at math. I can't add. I can't multiply. I once said 6 x 8 was 42. It kind of freaks me out that so many people ask me for math help. I'm basically on par with... um... a 6-year-old. So this book, Secrets of Mental Math, bound to be boring for someone like me, right? False! It's actually really interesting and totally NOT about Fermat's last theorem but about how to make everyday calculations like tax and tip easy to do in... well... your head. And the thing that freaks me out even more is that most of the strategies used to "be a genius and show off your math skills" are actually strategies that I use everyday to make my life easier! The only thing is, the authors, Arthur Benjamin and Michael Shermer, assume that the reader can do basic arithmetic. Well, they should publish a book called, how to make adding single digits more easily or multiplication tables for dummies that stick. I don't know. Despite my severe learning impairment, however, I was able to 1) learn a couple awesome tricks 2) find someone out there who breaks down math problems like I do and 3) amaze a couple friends... except for one friend, who didn't read the book, who got the answer faster than I did.... and by a couple seconds. Now a couple seconds might sound trivial to you, but... she sort of said the answer in a split second while I, straggling along, confirmed the answer 6 seconds later. Yeah, big delay, so much for impressing someone.

So, in order to impress, I'll have to sort of plagiarize the book, but only a couple tricks. I mean, the true beauty in this stuff is to share the magic or as Professor Benjamin says, "mathemagics."

What's 48 x 11?

I'll give you five seconds!

Was that too hard? (the answer is 528)

How about this one?

26 x 11

Quick! Two seconds!

Times up! Did you get it? (286)

So, how do you do these really quickly?

Well, the way I do it is

e.g. 89 x 11

89 x 10 + 89 = 979

But! Benjamin suggests this:

Condition: One of the two numbers being multiplied is 11

1) add the digits of the not-11 number

2) stick it in between the digits

3) if the sum of the digits is greater than 9, add 1 to the largest place and stick the (sum - 10) in the middle.

E.g. 23 x 11

2 + 3 = 5

Answer: 253

Ex. 2) 69 x 11

6 + 9 = 15

Answer: 759

And so on. Can this work for numbers greater than 2 digits multiplied by 11? Yes! Will I tell you? Well, I think any more than this would be considered plagiarism, so check out the book yourselves! http://www.amazon.com/Secrets-Mental-Math-Mathemagicians-Calculation/dp/0307338401.

I'm sure you'd greatly improve basic math skills! Be sure to know how to add/multiply single digits well! =)

No deep message to this blog message. =)

See ya later!

hehe