04.15.08
Mental soroban
I got and used a soroban as my primary calculator for some years. Once you learn the handful of basic combinations, you can add quite quickly—and addition was all I ever attempted, though the soroban can be used for the other arithmetic operations. I prefer the soroban to the Chinese abacus because of the soroban’s simplicity: 4 lower beads, one upper, in contrast to the Chinese style of 5 lower beads, two upper. The grandson has a soroban, but I’m not sure that he uses it. Perhaps he should watch this video, which I found on Callistonian.net.
