Japanese Multiplication.

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Japanese Multiplication.

#1  Postby Animavore » Nov 03, 2018 11:23 am



Pretty nifty.
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Re: Japanese Multiplication.

#2  Postby surreptitious57 » Nov 03, 2018 11:35 am


She was a bit slow

I did the second one in 48 seconds by the usual method but she only did it in 65
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Re: Japanese Multiplication.

#3  Postby I'm With Stupid » Nov 03, 2018 2:24 pm

I've seen this method before. I notice all the numbers have only 0, 1, 2 or 3 in them. Something tells me it doesn't work with numbers higher than that, or at least it becomes far more complicated.

But it's important to learn because as my maths teacher said to me, you're not always going to have a calculator in your pocket. Doh!
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Re: Japanese Multiplication.

#4  Postby Thommo » Nov 03, 2018 3:43 pm

It should work for any number, it's just going to be a real fucking mess when you have 9 lines crossing 9 lines.

If you think about it all that's happening is a group of lines represents a digit from 1 to 9, and its location left to right (slightly squiffy in the clip) represents a decimal position. Clearly the number of intersections of a group of n lines with m orthogonal lines is precisely n x m, and then you carry digits as normal.
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Re: Japanese Multiplication.

#5  Postby Animavore » Nov 03, 2018 3:43 pm

Didn't notice the numbers were all below 3. I haven't tried it yet and won't get a chance today.
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Re: Japanese Multiplication.

#6  Postby Animavore » Nov 03, 2018 3:45 pm

I'm With Stupid wrote:I've seen this method before. I notice all the numbers have only 0, 1, 2 or 3 in them. Something tells me it doesn't work with numbers higher than that, or at least it becomes far more complicated.

But it's important to learn because as my maths teacher said to me, you're not always going to have a calculator in your pocket. Doh!

Little did they know we'd have something more powerful than a (for then) PC.
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Re: Japanese Multiplication.

#7  Postby hackenslash » Nov 03, 2018 10:34 pm

I've seen this on one of the edchat accounts on twitter a while back. It does indeed work for any number, and is surprisingly neat as well.
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