Comments on: Extraordinary way to solve math problem

By: Yeah

Yeah — Sun, 13 Apr 2008 01:44:00 +0000

Oh yeah, it also works for numbers larger than 100.

101 * 102 = (100 – (-1) – (-2))*100 + (-1)*(-2)
= 10300 + 2 = 10302

By: Yeah

Yeah — Sun, 13 Apr 2008 01:35:14 +0000

This is based off multiplying two numbers of the form (100 – x). And so as long as you understand the method used, it will work for any number.

Let Z = 100 – y and W = 100 – x, then

Z*W = (100 – x) * (100 – y) = (100 – x – y)*100 + x*y

By: word

word — Thu, 13 Mar 2008 04:16:54 +0000

math sucks

By: Fine maths « Springblog08’s Weblog

Fine maths « Springblog08’s Weblog — Tue, 04 Mar 2008 21:00:02 +0000

[...] 4, 2008 at 9:00 pm · Filed under learning Did you know this way to multiply [...]

By: UncleCharlie63

UncleCharlie63 — Thu, 24 Jan 2008 07:37:20 +0000

Try 22 X 78. It doesn’t work.

By: me

me — Thu, 10 Jan 2008 14:58:15 +0000

“I agree with you, Toon. In that example you mentioned the method doesn???t work at all. Multiplying 43 with 37 gives 1591, which would give an overall answer of 201591. The actual answer is 3591.”

actually yes it would work if you do the last step a little differently. anything over the tens place in your product should be added…..so 1591 would be 15+20=35 then add your tens and ones to the end of it….3591

By: turk

turk — Mon, 07 Jan 2008 03:31:09 +0000

Interesting but useless. Old fashion way is faster. Faster way of multiplication is always the best way.

By: asdf

asdf — Sun, 06 Jan 2008 22:12:18 +0000

Bootstraps, the answer does work if you add 2000 to 1591. The “sticking a number before another number” method only works if the numbers, when subtracted from 100, multiply to 100 or less.

By: Jackolantern

Jackolantern — Sun, 06 Jan 2008 07:42:37 +0000

Give credit where it’s due. I’m pretty sure this is in ancient Hindu texts. It’s called Vedic Math, and this is simply one principle. There are tons more for different kinds of problems, involving different numbers, etc. There are even classes for this stuff, but it’s pretty rare. Amazing stuff really, thank the Hindus.

By: Matt`

Matt` — Wed, 02 Jan 2008 23:25:18 +0000

There was a strange method I saw ages ago and can’t remember the details of, where you could work out multiplications involving 7s 8s and 9s using your fingers.

Since every digit in the example is 7 or greater, it’s probably related, but taken up an order of magnitude (the thing I saw was probably based on the same idea, but using 10 in the place of 100)