On Sun, Oct 9, 2011 at 12:29 AM, Yoshiki Ohshima <yosh...@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 > _______________________________________________ > IAEP -- It's An Education Project (not a laptop project!) > IAEP@lists.sugarlabs.org > http://lists.sugarlabs.org/listinfo/iaep > -- Walter Bender Sugar Labs http://www.sugarlabs.org _______________________________________________ IAEP -- It's An Education Project (not a laptop project!) IAEP@lists.sugarlabs.org http://lists.sugarlabs.org/listinfo/iaep