# How Japanese Children Learn To Multiply [Pic]

Submitted by: ElectricEye 3 years ago in
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Japan: Where even the math is weird.
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Male 94
Common Core will just say that if you confuse the teacher enough and BS enough you can get 2+2=5 marked correct.
Male 38,494

I got stuck at `5`
Male 697
This is really old and not even that effective, simple long multiplication is easier
Female 1,205
the new way kids here are being taught to multiply is just freaking strange
Male 275
@Mikeoxdbiggg
Imagine quantum physics or simple integral methods.
I doubt I would come up with this by my self, but this appears quite "simple".
Male 7,775
@essersmith- Ah, I see it now, thanks.
Male 1,497
My question is how does someone sit down and hammer this method out? Imagine the trial and error beforehand.
Male 275
@Deyv well put.
Male 302
To be honest, this is good for teaching the concepts behind multiplication of multi-digit numbers in a way that naturally leads to polynomial multiplication. It`s just pointing out that the first one, 13*12, is equivalent to (10+3)*(10+2), then you distribute it to 10*10+10*3+10*2+3*2 which equals 156. Same for anything larger. 123*456 = (100+20+3)*(400*50*6)=(100*400 + 100*50 + 100*6 + 20*400 + 20*50 + 20*6 + 3*400 + 3*50 + 3*6)= 40000 + 5000 + 600 + 8000 + 1000 + 120 + 1200 + 150 + 18 = 56088. The concept expands to polynomial multiplication since everything so far has just been polynomial multiplication with single digit coefficients and with x=10. So if x=10, then (327*151) = (3x^2+2x+7)*(x^2+5x+1)= (3x^4 + 15x^3 + 3x^2 + 2x^3 + 10x^2 + 2x + 7x^2 + 35x + 7) = 3x^4+17x^3+20x^2+37x+7. Plugging 10 back in for x, 30000+17000+2000+370+7 = 49377.
Male 4,746
Slow and crude. I think the way we do it is much more efficient.
Male 466
This is called Vedic maths.
Its actually from India.as a kid I could use this method before I learned the western method.
My teachers actually graded my work as an F once because even though my answers were correct, I could not show them my working out.
Male 275
@drawman

They count the number of times lines cross eachother. They go left to right, counting diagonally. So 1, 5, 6. Means that top left the lines cross 1 time. middle diagonal they cross a total of 5 times and bottom right cross 6 times.

The numbers represent digits and 1`s, 10`s, 100`s and so on. going from high to low. The 1 represent 100, 5 represent 50 and the 6 representy 6.

If the lines add up to say 12. Then, given the lines location, it represents 12, 120, 1200 and/or so on.
Try to apply it to the slightly larger calculation. It makes sense, in a japanese kind of way.
Male 7,775
So is someone going to explain?
No one I always hated mathS.
Male 275
Lets try again:

996 * 693 = 690228
Less than a minute to do by "old fashion" hand calculation. This is slow aswell I suppose.

About 2 minutes with the japanese system.
Id love to see a japanese person do this, I presume the drawing of the system becomes less needed once you get used to it.

Male 275
Crud, I miscalculated, I didnt count the blue lines!
Male 275
@Nickel2

553 * 352 = 194656

I tried it the japanese way. Perhaps once you are very familiar with the system its fast. But it took me longer to sit and count and add than it took the way I was taught.
Male 5,874
The Scots are well known for being calculating...

Male 172
this is extremely cool and easy! Ive learned this before in school.
Female 232
I want to learn how to do this! Just... because.
Female 2,927
wait...what? what the hell are the blobs even for?
I cant...I dont even...what?
Male 977
geomegebra. i love it.
Male 2,675
whoa.
Male 14,835
We`ve covered this method here before
Female 1,467
I prefer long division and long multiplication when doing things by hand it`s easier/quicker for me to double check.
In my head I prefer weird approximations or dealing with fractions.
Male 662
The calculator is Korean not Japanese.
Male 26
FoolsPrussia: I don`t think he means that kind of multiply.
Male 3,061
Female 6,381
That`s hardly what I would call a shortcut. 8-\
Male 3,445
Aren`t children a little young to multiply?
Male 46
Looks like a different representation of what we do: multiply every digit of the first number with every digit of the second. But the way it makes it so visual is pretty neat indeed.
Male 2,729
Link: How Japanese Children Learn To Multiply [Pic] [Rate Link] - Japan: Where even the math is weird.