[IAEP] Abacus suggestions

Walter Bender walter.bender at gmail.com
Sun Oct 9 15:11:24 EDT 2011

On Sun, Oct 9, 2011 at 12:29 AM, Yoshiki Ohshima <yoshiki at vpri.org> wrote:
> For the first time I launched Abacus activity today.  My impression is
> biased as I am Japanese and learned a version of it at school, but
> here is some suggestions:
>  - The graphics lacks essential "dots".  You see some dots in this
>    picture for example: http://kamedake.com/_src/sc946/DSC_1976.jpg.
>    These are "period" and "commas".  The big white two dots means the
>    it is 1's digit.  The smaller dots on the bar are put every 3
>    digits; even though the Japanese writing system would work better
>    with comma's every 4 digits, we conceeded to westerners.  In any
>    case, missing these dots was the first surprise for me.

Would it make sense then to let the user move the dots left and right
depending upon where they want the 1s digit? Or is it always in the
same place?


>  - As you can see, the default 1's digit (the big white dots) is in
>    the middle, not the far right.  That makes sense to tell that
>    there are numbers smaller than 1 and for the idea of power of 10.
>    (It is often a good technique to slide the decimal point, so I
>    first thought the red triangle to mean this, but it is something
>    else.)
>  - It trys to show the addition on the bar, but it defeats the whole
>    point of abacus.  Instead of showing:
>       700 + 10 + 7 = 717
>    We would put just one number at each column and then the result
>    should be self explanatory.  (It would show "7 1 7" and it is the
>    result.)
>  - For a non-"5 and 4" abacus, this is not simple, but then why kids
>    in the 21st century need to learn Mayan arithmetic...
>  - So, there are some 90 combinations of two one digit number
>    additions.  Some require 5's compliment arithmetic (adding 4 to 2
>    is subtracting 1 but then adding 5, etc.) or 10's (if it is the
>    right terminlogy.)  Abacus was about building the muscle memory
>    for these 90 patterns of additions.  Some of these require you to
>    move both index finger and thumb at the same time.  After
>    acquiring this muscle memory, you can do any additions without
>    thinking, and that is the point of abacus.  But now, "doing
>    additions without thining" is easier with electronic calculators.
>    At the same time, the Abacus activity is not set up for learning
>    about this part of idea (and XO is not multi touch, so you can't
>    build the muscle memory).
>  - However, it is still valuable to be aware fo the idea of
>    understanding the idea of "adding 4 is adding 5 but subtracting
>    1", etc.
> ----------------
>  - There is a bug when I tried to make my own abacus.  If there is a
>    number already on abacus, changing the board made some beads stuck
>    outside.
> -- Yoshiki
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Walter Bender
Sugar Labs

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