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Solve large # multiplication in less than 10 seconds

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.MintBerryCrunch
Posts: 750 - Karma: 346
So I'm a double major in math and accounting and somehow had never heard of this before today, go figure. You may already know this method but for those of you who don't here is an easy way to make yourself intelligent.

Take 93 and 98 for example. We establish that 100 is a good baseline for both of these numbers. 93 is 7 away from 100 and 98 is 2 away from 100.

This leaves us with two integers -7 and -2. 98-7=91 and 93-2=91. This gives us the first two digits of the solution (91).

Now we multiply these intergers -7*-2=14. This gives us the final two digits of the solution (14)

9114


Jun 23 2011 11:06PM
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soulskier
Posts: 17805 - Karma: 3,821
fuck that, i'll make a copy
Jun 23 2011 11:07PM
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schism
Posts: 1705 - Karma: 389
why on earth would you want to major in math?
Jun 23 2011 11:08PM
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swd
Posts: 475 - Karma: 12
My calculator would still beat me
Jun 23 2011 11:08PM
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KravtZ
Posts: 6637 - Karma: 2,629
make lots of money...lots of options
Jun 23 2011 11:10PM
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ridearmada14
Posts: 441 - Karma: 18
this

p.s. that just fucked my mind
Jun 23 2011 11:10PM
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JakeAssBeatClap
Posts: 6673 - Karma: 2,535
do it with 1243 and 65..
Jun 23 2011 11:14PM
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Pee_and_Ski
Posts: 1869 - Karma: 57
math is for asians and smart people, not skiers come on now guy
Jun 23 2011 11:15PM
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Get.Kronk
Posts: 2543 - Karma: 226
85x75

75-15=60
85-25=60

15+25=40

So 85x75=6040?
Nope, It's 6375

I think I did that correctly by your method.
Jun 23 2011 11:16PM
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SkiFreshPow
Posts: 233 - Karma: 334

I tried 78 and 77 with 80 as a base.

thats 77 -2=75   ans 78-3= 75

then -2 x-3 = 6

I either get 756 or 7506 but neither is the correct answer, which is 6006

either this dosent always work or I did something wrong.

Jun 23 2011 11:16PM
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los.pinguinos
Posts: 555 - Karma: 34
and your mom
Jun 23 2011 11:17PM
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.MintBerryCrunch
Posts: 750 - Karma: 346
shit you're right, well, I don't know all the rules about it but I'll try and figure it out I guess
Jun 23 2011 11:21PM
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bangarangmules
Posts: 5065 - Karma: 84
Man I still couldn't even follow that...given I looked it over quickly. But still.
Jun 23 2011 11:21PM
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theJones
Posts: 676 - Karma: 158
multiply 15*25 gets you 375, add it to 6000. the first 2 last two thing only works if the 2 numbers multiply to double digits. Otherwise assume 60 is short for 6000 and add the second part.
Jun 23 2011 11:22PM
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ridearmada14
Posts: 441 - Karma: 18
some math major u are
Jun 23 2011 11:30PM
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darsh.
Posts: 370 - Karma: 8
FUCK MATH. WE SKI
Jun 23 2011 11:31PM
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theJones
Posts: 676 - Karma: 158
just doing it in my head, I think the base always has to be 100. If you do that then you get the correct 6006, and every other base gets you a different answer.
Jun 23 2011 11:31PM
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AwR
Posts: 5147 - Karma: 1,878
I majored in math and actually teach it. This is always a neat trick to play with kids to trick them....or bet money on it.
Jun 23 2011 11:37PM
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Blindsurfer
Posts: 2252 - Karma: 2,785
i think the proper base here would be 70 or 75
Jun 23 2011 11:39PM
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JosephStalin
Posts: 1673 - Karma: 100
mytreds
Jun 23 2011 11:46PM
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Get.Kronk
Posts: 2543 - Karma: 226
oh yep, idk why i added those two
Jun 24 2011 12:03AM
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ORDEAL
Posts: 6386 - Karma: 75
I would love having you as a math teacher... yet absolutely hate it. Teachers who fuck we me every day piss me off
Jun 24 2011 12:05AM
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BE..
Posts: 1185 - Karma: 81
If only this were true....
Jun 24 2011 1:43AM
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Mr_Orange
Posts: 1024 - Karma: 154
cool i'm gonna use this.

but for your's in particular, since 98 is so close to 100 I would do it in my head like this...

93*100= 9300 then (93*2) or 186 so 9300-186= 9114


im gonna try one

67*86

5300 + 14*33.......times 14by 10=140, then times 3 (because 30) = 420 + (14*3) =462

answer: 5762 i think

yaaa your method works very well for some but others you can write it down on paper and do it in 10seconds vs stressing your brain

and as for the calculator comments, ive taken two math courses at university neither of them permitted calculators
Jun 24 2011 2:58AM
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Mr.Turtle
Posts: 3690 - Karma: 96
lol figured this out 6th grade
/claim?
Jun 24 2011 4:32AM
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Lemuel
Posts: 14477 - Karma: 10,515
Easy to get a job
Million different job options
Very useful skill
Payed alot of money
Not a very popular major


Jun 24 2011 9:11AM
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schism
Posts: 1705 - Karma: 389
all very valid points I suppose.

I would still never major in math, just not my cup of tea. I would want to major in something that I like/find interesting, i guess the OP finds math interesting enough to do so.
Jun 24 2011 10:29AM
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BIGben*
Posts: 1942 - Karma: 8
A double math major? Props for posting that on nS... But srsly, it doesnt wprk and i could just use my calculator?
Jun 24 2011 10:48AM
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Otter.
Posts: 1161 - Karma: 84
thats what my ti-84 silver edition is for..
Jun 24 2011 12:14PM
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