[IAEP] Abacus suggestions
Yoshiki Ohshima
yoshiki at vpri.org
Sun Oct 9 00:29:51 EDT 2011
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.
- 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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