# [IAEP] Abacus suggestions

Walter Bender walter.bender at gmail.com
Sun Oct 9 08:57:51 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.

I wasn't aware of this. (We should update the Wikipedia article on the Soroban.)

>
>  - 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.)

The red triangle is a mark found on many Chinese abaci. It is useful
for to keeping track of place while doing multiplication and division.
>
>  - 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.)

This is a very good idea.

>
>  - For a non-"5 and 4" abacus, this is not simple, but then why kids
>    in the 21st century need to learn Mayan arithmetic...

My goal with the abacus was primarily to introduce the idea of
multiple representations.

>
>  - 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).

I haven't played with the abacus on the touch-screen XO yet... but it
is not multitouch. Muscle memory is not something we can do much with
on that hardware :P

>  - 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.

Yes.

>
> ----------------
>
>  - 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.

I thought I fixed that bug in a recent release. What version are you using?

Thanks for the feedback. Regards.

-walter
>
> -- Yoshiki
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>

--
Walter Bender
Sugar Labs
http://www.sugarlabs.org
```