This may be old... But I figured some of you might enjoy it - or figure out a way to discredit it...

Either way, it is pretty interesting.

http://www.ted.com/index.php/talks/view/id/199

4/28/2008 11:57:49 PM

THINK OF A NUMBER BETWEEN 10 & 20, ADD THE DIGITS TOGETHER, & SUBTRACT THE SUM FROM THE ORIGINAL NUMBER

ABRACADABRA

9

OMG I'M A MATHAMAGICIAN

4/29/2008 12:03:57 AM

unless the audience was planted it was impressive

4/29/2008 12:10:31 AM

guy is kind of conceited about this "tricks"

Quote :

"Thank you every much!"

4/29/2008 12:11:05 AM

ted comes up with some neat stuff

4/29/2008 12:11:57 AM

4/29/2008 12:15:07 AM

Otherwise unrelated, but I just happened to watch this video on TED's site the other day: http://www.ted.com/index.php/talks/view/id/24. It's an amazing modern dance duo routine.

I know most people on here could really give a fuck about modern dance, but I thought I'd link that for the few people who enjoy a bit of culture or have maybe already heard of TED on their own.

[Edited on April 29, 2008 at 1:19 AM. Reason : ]

4/29/2008 1:12:37 AM

I thought this was about Donald Duck in Mathemagic Land

4/29/2008 1:16:42 AM

He has an earbud in his right ear. Someone could be feeding him the answers remotely.

[Edited on April 29, 2008 at 1:26 AM. Reason : not that someone couldn't learn what he was doing anyway]

[Edited on April 29, 2008 at 1:26 AM. Reason : ]

4/29/2008 1:24:17 AM

he's a magic man.

4/29/2008 1:28:53 AM

maybe im wrong (which is more likely than him, i SUPPOSE)

but i swear he fucked it up at the 3:40 mark, check it out --
he said that:
(457*457) = 205,849
(457^2) = 205,849

but really the answer is:
(457*457) = 208,849
(457^2) = 208,849

does he address this anywhere later? i kinda stopped being impressed when he messed up and stopped it maybe he did it on purpose?

still impressive though.

its funny. a decent amount of people are impressed that i can do 'easy' math in my head without a calculator. nothing like that. just 2 digit add/subtract/multiply kind of stuff

dont think im a math wizard at all. was always ok with it at school. always made As in HS and college in math (pretty much my only A's in college were math).... but i always had to do the homework and learn it etc.

that would be a neat method to learn (unless its freaking memorization), but i dont see it getting me anywhere in life

4/29/2008 1:34:45 AM

yeah, he got it wrong, said 8 instead of 5, but still the whole thing was pretty impressive

4/29/2008 1:45:51 AM

but seriously

that shit's fo real

there's some tricks I learned a while back that I often use (when possible)


in your head, determine these products

279 * 311 = ?

965 * 735 = ?

know the tricks? (I'm sure you know some of them)

4/29/2008 1:55:55 AM

i went to this math competition in highschool where the main event was the teams competing against eachother in this timed thing where you only had like 30 seconds to do a problem, and they were all tricks. the problem was the other schools had actual teams and shit that practiced these, and my school just threw a team together the week before. we got our asses handed to us so bad, but they gave us free pizza afterwards so it was good.

4/29/2008 1:58:47 AM

I was in the debate club

and even I look down on you math fags

4/29/2008 2:54:38 AM

Quote :

"Mathamagician"

Mathamatics?

4/29/2008 7:48:05 AM

Quote :

"i went to this math competition in highschool where the main event was the teams competing against eachother in this timed thing where you only had like 30 seconds to do a problem, and they were all tricks. the problem was the other schools had actual teams and shit that practiced these, and my school just threw a team together the week before. we got our asses handed to us so bad, but they gave us free pizza afterwards so it was good."

me too.

there was this one problem where we had to construct some 10-sided polygon or shit, so we just put down ABCDEFGHIdon'tgiveadamn.

4/29/2008 7:51:51 AM

Quote :

" was in the debate club and even I look down on you math fags"

jealous much?

jk

I took debate class, but was never in the club -- I was, however, an "alternate" for the iq-team

I think everyone [highschoolers] should have to take speech and debate class

that class, and the idea of arguing both sides of an issue, changed my life and my understanding of the world



anyway

Quote :

"279 * 311 = ? 965 * 735 = ?"

everyone knows to remove zeros when multiplying, then appending them back to the product

70 * 30 = 7 * 3 + "00" = 2100

most everyone knows that multiplying consecutive numbers is a square plus the remaining factor

25 * 26 = 25² + 25 = 625 +25 = 650

also, there are some addition/subtraction tricks that ease calculation (not always starting with the 1's place, then 10's, etc)

7976 - 239 = 7976 - 230 - 9 = 7746 - 9 = 7737

a lesser know trick is used for calculating squares of integers that end in "5"

Z5² = Z * (Z+1) + "25"

115² = 11 * (11+1) + "25" = 11 * 12 + "25" = 13225

and my favorite (although not always helpful,) is used for multiplying two even or two odd integers

such pairs can be expressed as an integer plus-or-minus another integer

and then it (remember algebra?) can use the "difference of squares": (x+y)*(x-y) = x² - y²

17 * 23 is 20 ± 3, or (20+3)*(20-3), which is 20² - 3², or 400 - 9 = 391

OMG COOL!


then, simply combine the tricks:


279 and 311 is 295 ± 16

295² is 29 * 30 + "25", or 30² - 30 + "25", or 87025

16² is 256

so 279 * 311 is 87025 - 256, or 87000 - 231, or 86769

so, 279 * 311 = 86769




965 and 735 is 850 +- 115

850² is 85² + "00", or 8 * 9 + "25" + "00", or 722500

115² is 11*12 + "25", or 13225

so 965 * 735 is 722500 - 13225, or 722500 - 13200 - 25, or 709300 - 25, or 709275

so, 965 * 735 = 709275




[/YOUR CALCULATOR IS MAKING YOU DUMB]

4/29/2008 11:12:20 AM

this is pretty rad too.
http://www.ted.com/index.php/talks/view/id/78

4/29/2008 11:38:05 AM

^ that was entertaining

4/29/2008 11:58:53 AM

I don't think that word shit was an illusion ...

4/29/2008 12:04:45 PM

HEY GUISE HEREZ A MATH TRICK

PICK A NUMBER

MULTIPLY IT BY 2

SUBTRACT THAT NUMBER BY YOUR ORIGINAL NUMBER

OMG IT'S UR ORIGINAL NUMBER LOL ABRACADABRA

4/29/2008 12:19:16 PM

4/29/2008 12:19:50 PM

ONE TWO THREE FOUR FIIIIIIIIIIIIIIIIIVE!!!!

lol, crazy kid

4/29/2008 12:25:38 PM

what the fuck is wrong with that kid?

4/29/2008 12:27:14 PM

this is dumb, its mostly tricks, im not at all impressed

4/29/2008 12:33:37 PM

^^^^haha that video is fucking hilarious

4/29/2008 1:32:33 PM

he needs an ass whoopin

4/29/2008 1:35:23 PM

Quote :

"SUBTRACT THAT NUMBER BY YOUR ORIGINAL NUMBER"

SUBTRACT FROM

NOT

SUBTRACT BY

4/29/2008 3:47:14 PM