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Thread: Japanese multiplication technique - GIF

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    Supporting Member Frank S's Avatar
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    Jethro from the Beverely Hillbillies, naught and naught and naught plus naught equals 42. Now haw he ever came up with 42 is anybody's guess

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    He was prescient about HHGTTG?

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    Supporting Member Frank S's Avatar
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    Quote Originally Posted by kb4mdz View Post
    He was prescient about HHGTTG?
    Yep, but his brain probably ran on granny's rheumatiz medicine not lemons
    Never try to tell me it can't be done
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    Looks nice. Try 76x47...

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    shows how numbers over 10 intersections are dealt with

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    So basically abacusless abacus?

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    Quote Originally Posted by jarekp View Post
    Looks nice. Try 76x47...
    Or 99 x 99.

    Gonna be drawing a lot of lines and counting a lot of intersections. I fail to see any advantages to their system.

    99 x 99 = (100 -1) x (100 -1) = 100 x 100 - 200 + 1 = 9800 + 1 = 9801

    would seem a lot simpler - can even do that one in your head.

    76 x 47 = (80 - 4) x (50 - 3) = 4000 - 240 - 200 + 12 = 3560 +12 = 3572

    Ok, a bit more difficult but still simpler than drawing all those lines.
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    Or having paper, "western" oldschool method:


    76
    47
    --------
    532
    304
    -------
    3572

    At least no limits of digits.

    Btw
    Have you imagined that Copernicus was able to do quite complicated calculations?
    Try to do above using roman numbers (he did not know other)....
    J.

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    Quote Originally Posted by jarekp View Post
    ...
    Have you imagined that Copernicus was able to do quite complicated calculations?
    Try to do above using roman numbers (he did not know other)....
    The awkwardness of computation using Roman numerals probably accounts for the Romans' use of the abacus.

    The Roman abacus was similar to modern ones but had some additional columns at the right...

    Japanese multiplication technique - GIF-roman-abacus-c1ad.jpg

    The Wikipedia article provides a full description of the device and its use...

    https://en.wikipedia.org/wiki/Roman_abacus
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