My Dry-Erase Board And A Math Trick!
December 10, 2009 by
Filed under dry erase board
How to square a number that ends in 5. Without a calculator.
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That will come in very useful in my Physics class.
yea..if u read the info and listened he said that it’s only for numbers that end in 5
but the square of 12 is 144 while in ur way is 24 is that onnly if the last number is 5??? nice try!!”=)
nice vid, the sound quality wasn’t the greatest though
does 777 edd with 5?
ok i take that back..777×777 dosent work…..why dont you get high off that dry erase marker you virgin for life
wow thats awsome
Hey, thanks! I’d never seen it proven before.
Proof for this trick…
ab * ac where ab & ac are two-digit numbers, and b+c=10.
In reality, (10a+b)(10a+c) = 100a^2+10ac+10ab+bc
Some reverse distributing, 10a(10a+c+b)+bc
Since b+c=10 and b+c=c+b, then 10a(10a+c+b)+bc = 10a(10a+10)+bc = 100a(a+1)+bc.
This trick is only a corollary of that general rule the gentleman instructed upon.
it is only with the 5 at the end? i tried 72*72
it works for any double digit numbers, with the 1st digits being the same and the 2nd digits summing up to 10.
ie. 43×47, just multiply 1st digit by next higher (in this case 5, so 4×5=20), and write the product of the last 2 digits (in this case 3×7=21)
and there you have it,
43×47=2021
hmmm… not very interesting… much better the hot chicks from LikeHerAss.com_
see how a hot chick loses a bet and has to strip in front of her classmates (_stripAss.com_)
I see I’m not the only one who thinks so. Wish I could write with cool flourishes like that.
Oh, nice math trick, too.
)
well, does 777 end in 5?
Awesome!!!
fuck off u twat, i knew this years ago
it indian vedic math, stop stealing our stuff u honkey
Try 777×777 it does not work guys!
Ummm this only works with the last digit being 5
im going to tell my math mate about that, he’ll love it
nice. i’ll use that for the number sense test
Wo….your hand writing is amazing!
Wow… Cool..I love math tricks.. Hey, I like your handwriting style. Mine is like chicken scratches!
That was a good one.
Nice, Have you ever heard of the rule of 72? That one can make you wealthy.