Adding and subtracting with the Japanese abacus
Let’s say we start with the number 3. Remember to use your thumb for the 1 – 4 beads.
Now we want to add 1. You move one bead up
Then, to add 5 we use our forefinger to move the 5 bead to the bar.
So now we have 9. We want to add a 7. First take away 3 (the blue arrow), then add 10 (the green arrow). Why this way and not the 10 first followed by the 3? Because you first have to see if you’ve got an available 7 in the 1s column. If you haven’t then you know you have to subtract 3 and add 10.
Finally let’s take away 12. First the 10, then to take away 2, you’ve got to shift the 5 up as well as the 3, so you do these simultaneously.
So now you know how to add and subtract. In a later article, I’ll teach you the principles of multiplication.