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Japanese Multiplication
Posted: Wed Jan 16, 2013 7:40 am
by idle
Some one posted a picture of how the Japanese teach kids to do multiplication on Facebook
and I thought wow that's a great method to teach.
a vid of the method here
http://www.youtube.com/watch?v=zPmrKtIhf_I
and a quick and dirty bit of code to do the same no idea what it's limits are.
Code: Select all
EnableExplicit
Procedure.s jmul(sa.s,sb.s)
Protected lenA,lenb ,lenC,a,b,c,ct,v,r,sout.s
lenA = Len(sa)
lenB = Len(sb)
lenC =(lenA+lenB)-1
Dim mat(LenA,lenB)
Dim sum((lenA*lenB)-1)
For a = 1 To lenA
For b = 1 To lenB
mat(a,b) = Val(Mid(sa,a,1)) * Val(Mid(sb,b,1))
If a > 1 And b < lenb
mat(a,b) + mat(a-1,b+1)
EndIf
Next
sum(a) = mat(a,1)
Next
ct = lenA+1
For c = 2 To lenB
sum(ct) = mat(lenA,c)
ct+1
Next
For c = lenc To 1 Step-1
v = sum(c) % 10
r =( sum(c) - v ) / 10
sum(c) = v
sum(c-1)+r
Next
For c = 1 To lenc
sout + Str(sum(c))
Next
ProcedureReturn sout
EndProcedure
MessageRequester ("Japanese Multiplication",jmul("10000000000000000000000000000000","10000000000000000000000000000000"))
Re: Japanese Multiplication
Posted: Wed Jan 16, 2013 9:04 am
by davido
Thanks, idle.
A very nice demonstration coding.
Hardly related but have you seen the virtual abacus method?
Re: Japanese Multiplication
Posted: Wed Jan 16, 2013 12:10 pm
by idle
Thanks, It just struck me as a very interesting method to teach multiplication that's both quick and easy
plus it's probably useful for later on when they introduce linear algebra and tell them they've been doing
it all along since primary school.
The big O of the algorithm isn't that bad either.
No haven't seen the virtual abacus method do you have a link?
Re: Japanese Multiplication
Posted: Wed Jan 16, 2013 3:22 pm
by American Ninja
Seems very slow to me, and needs lots of paper space. And what happens if they need to do the math in their heads???
Re: Japanese Multiplication
Posted: Wed Jan 16, 2013 8:34 pm
by Nituvious
I understand that method but seems tedious for larger numbers.
Re: Japanese Multiplication
Posted: Wed Jan 16, 2013 9:38 pm
by idle
What can I say?
The algorithm has a shorter time complexity with a reduced number of additions and carries
than the method we're commonly taught.
Code: Select all
1 1 1 2 3 4
2 * 2 2 4 6 8
3 3 3 6 9 12
4 1 1 1 1 <-carrys
1 5 1 7 8 2
Re: Japanese Multiplication
Posted: Wed Jan 16, 2013 10:48 pm
by davido
Hi idle,
I mentioned the virtual abacus on the spur of the moment, recalling that I had seen this on the UK news channel some years ago.
The report showed young children from an eastern country, probably China. These children were taught to use the abacus and when they became proficient the abacus was taken away and the calculations done by moving their fingers as if using a real abacus. Later they didn't even have to move their fingers. And they were very quick, even for large numbers.
I expected you might find this easily on You Tube for instance. Hm... not so easy.
This is the nearest I could find:
http://www.youtube.com/watch?v=s-EKxq1oTPw
Thanks again. Nice to learn something new and interesting and a free PB demo coding!
Re: Japanese Multiplication
Posted: Thu Jan 17, 2013 3:27 am
by idle
that's why I asked you for info on it a search didn't turn up anything significant
Re: Japanese Multiplication
Posted: Thu Jan 17, 2013 8:41 pm
by Inf0Byt3
I have seen a similar thing in a documentary on TV, some time ago. I think the students were Japanese, and as Davido stated, after some years of training they could use an "imaginary" abacus to do the calculations. We might have seen the same video. Couldn't find the original clip, but this shows something close to it:
http://www.youtube.com/watch?v=hmRXh3ApswM
Re: Japanese Multiplication
Posted: Fri Jan 18, 2013 8:25 am
by idle
yes that's generally how they do it.
I worked out how to do a div with the method but haven't got time to do it
right now.