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A Clever multiplication trick


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This has absolutely nothing to do with Armenians, but what the heck, we need a change of pace once in a while. Here is a way you can multiply any two digit number by 11:

 

Example: 23 x 11

 

Change the 2 to the hundreds place, leave the 3 where it is and leave a blank space for the tens place

 

2_3

 

Now add the two digits

 

2 + 3=5

 

And place the sum in the tens column

 

253 This is your answer to 23 x 11!

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My first immediate reaction when I saw this was, "Oh No! I've had just about enough of mathematics to last a lifetime! (We have to do lots of it in the course I'm in, you see), No more! But I'll do a bit to humour him"

 

But when I saw it it looked funny and intersting! Let me try it....12 * 11 1-2 1+2=3 123 12*11=123

 

How'd you find that one out?

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Im a sixth grade teacher, and am constantly trying to find things to spark my students' interest. I learned this at a Math In-service. There is also a neat way you can multiply with any digits using squares that you draw on your paper. I wish I could show how! Also you can multiply any number by 9 by simply adding 0 to the number then subtract the number you want to multiply by 9. Like this

 

78

x 9

 

 

780

-78

702

 

Of course this takes longer, but its neat to show that there are different ways to solve problems.

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I don't mean to pipe in on every friggin' thread here but....math is my profession. I have a bachelors in math/statistics. I'm an actuary; we are the numbers guys/gals for the insurance industry. Feel free to flame me if your auto rates have gone up lately.

 

Kazza, if you have any specific questions, I love tutoring. Just hope I can answer 'em...

 

[This message has been edited by Pilafhead (edited October 11, 2000).]

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Teachers? (not the whisky)

 

I just love that other problem you did! I shall need to try that, seriously now, because I struggle a LOT woth my multiplication tables ESPECIALLY 9's, and the basics. I am completley apush at it. The advanced theory stuff I'm good at, with a calculator! But I could be better because the not knowing basics slow me down. I didnt vochinch hard enough at baby school. Because I am doing computer science, programming, and natural sciences, inevitably that involves maths. So pilaf head, you have literally saved my life bro

 

Farsi Jan, what is an in-service?

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My father taught me that trick of yours when I was much younger and I still remember it!! lol...I just wish I retained everything my father taught me and still teaches me, I think I'd be much better off.

 

Steve, I think it's adorable you teach six grade. I work with kids myself (in special ed.) and it's not everyday you come across a teacher who happens to be a man, so the mere mention of a male teacher makes me melt. I don't know if you plan to make a career out of it, I hope you do

 

Gayane

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Gayanne babe,

 

That's a coincidence! I want to work in teahing myself, but teaching special ed.

 

I think that's already his career.

 

At my old school there were plenty of male teachers, but i dont know if times have changed now.

 

Anyway. Keep all the fun posts coming!

 

P.; where is Artur lately? I havent seen him round here. Maybye he's gone on too many feminist marches.

 

Laters

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Kazza, an inservice is a workshop/class offered to teachers to help them develop better professionally.

 

Gayane, wow, thanks! I love teaching and kind of fell into it. I plan on continue teaching for a long time.

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