Brian Foley

Multiplying by Nine with the Finger Method



Posted: Monday, November 24, 2008

by
Magic and Learning

Can you do the nine-times tables on your fingers?

When you learn how, you'll never have to stare at the multiplication tables charts for nine again. The best part is, you only need to be able to count in order to learn this!

And if you practice using the finger method, you'll be a whiz at multiplying any digit by nine, and never have to "guess" and hope you're right again.

You can learn it now, in a few simple steps that you'll never forget. But you must remember that it is not meant to be a crutch. You must practice it a lot in order to get it to the point where you don't need to do it on your fingers every time you want to multiply by nine.

At the end of the article, you'll find a great, free resource where you can find a fun way that will make you love to practice it, and it will also teach you why the method works.

Let's get down to multiplying:

First, you have to number each of your fingers. With your hands palms down, thumbs almost touching, start from the left and call your L. small finger, "one." The L. ring finger is "two," the L. middle finger is "three," etc. until you get to the R. pinky, which is "ten."

That was easy!

Now, to multiply any digit by 9, you simply bend the finger that has that number inward. In other words, if you were to multiply nine by three, you'd bend the "three" (that's the L. middle finger). Bend it inwards, beneath your hand.

Notice the number of fingers on the left of the finger that's bent. There should be two of them. That's how many tens there will be, making the answer, "twenty-something."

Next, notice the how many fingers are on the right side of the finger that's bent. There should be seven of them. That's how many units there will be, making the answer, "twenty-seven."

That's it. Your done!

Warning! - This should not be used as a "trick." Don't make it a crutch. Practice it until you know the "nines-times-tables" by heart. If you still need to use your fingers after a day or two to practice, then you really haven't practiced enough.

There is a "master method" for using your fingers to learn to multiply. You only need one method for all the numbers from 6-9, so you don't have to learn a bunch of different "multiplication tricks."
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Brian Foley (a.k.a. "Professor Homunculus") is the creator and web manager of Math Mojo and TheMath Mojo Chronicles. He's presented his Math and Magic programs at schools, corporations, and other facilities throughout the U.S. and Europe.

Brian Foley (a.k.a. "Professor Homunculus") is the creator and web manager ofMathMojo.com andThe Math Mojo Chronicles.He's presented hisMath and Magic programs at schools, corporations, and other facilities throughout the U.S. and Europe.


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Top-level comments on this article: (4 total)
» left by straight talk
3 years 65 days ago.
111 fans. Follow straight talk on twitter!
Any help one can provide the multitudes that struggle with basic math is helpful and appreciated.
» left by Dianne Lehmann
3 years 53 days ago.
133 fans.
Hi Brian.
 
That's just weird. I went to grade school in the 50's and 60's so I had the times tables drilled into me until they were pretty much hard wired, but I love this little trick.
 
I have also loved the number 9. That whole 9 x 2 = 18 and 1 + 8 = 9 thing always seemed like magic to me. It works for anything times 9 (9 x 27 = 243, 2 + 4 + 3 = 9). In addition you get 9 + 2 = 11 and 1 + 1 =2. Cool.
 
I think the best way, like yours, to teach kids about numbers is to let them have fun with them.
 
Dianne
» left by creativeblogger
3 years 51 days ago.
multiplying by nine is the easiest of all numbers to multiply

simply add a zero to the end of the first number and then deduct the first number.
 
Ie
 
250 x 9 =
 (add the zero)
2500
 (deduct the first number)
2500 - 250 = 2250
 
to multiply 9 by smaller numbers
 
simple remove 1 from the multiple number and then add digits so together they total 9
 
ie:
 
7 x 9
 
(deduct 1 from 7)
 
= 6

( 9-6 = 3)
 
ie, 7 x 9 = 63
 

» left by LeahG Artist 3 years 51 days ago.
192 fans. Follow LeahG Artist on twitter!
The Trachtenburg system of mathematics (basic maths) will teach you how to do any math in your head in seconds. I wish they taught it in schools.
» left by Brian Foley 3 years 51 days ago.
3 fans.
I taught myself Trachtenberg speedmath in my thirties. It is an amazing system, and Jakow Trachtenberg was in inspiring figure.

Like any system, it is not complete, and there are many other things that are important to learn in speedmath, but it is the best basis I can think of. Schools should teach a lot of different methods, because it is about asking questions, like "why does this or that method work that way, and what can I learn from it?"

You can find out more about this at: The Math Mojo Chronicles.
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