# Soroban and Anzan

(Rose) #41

Thank you Kinma for sharing your experience.
Luck you to have a such a wise father. I have a question for you. When I see my son using the Soroban, for exemplo to do a -8. We should add 10 and then take 2 on the unit rod. Work from left to right. And sometimes he does the reverse. Do you think this is detrimental to his mental Soroban? I know this might slow him down the road, but he always get to the right answer. Thanks

#42

Best is indeed to work from left to right and always do this the same way. It is not bad to work from right to left. Not even to mix them up and mix left to right with right to left, as long as you don’t forget to do all rods and take care of any carries…

However; for automation, which is needed for speed, it is best to ALWAYS do it the same way.

At some point he will realize that he reaches a speed limit if he wants to do this very fast. Also if he wants to do more digits.

There is also a little trick that you can do to force him to do it from left to right, always. Ask him to call out the intermediate results.

Let’s say his answer is 355, calculating 122+233.

If he starts from the right he cannot call out the number until he is done.

However; If he starts from the left, he can call out “three hundred” right after completing the first rod. There might be a carry from the tens into the hundreds. In that case just let him call out 300… oh no, 400…

Later you can teach him to look ahead, so he can expect a carry.

This way might also prepare him for 4 digit mental calculations since he can already do this on the physical soroban.

The funny thing is that while typing away I get ideas. So let’s ramble on a bit.

He says he finds 4 digits too hard.

Also tell him that he can forget about that specific rod after he is done (later he will remember more rods at the same time).

So he does 1,000 + 2,000, calls out “3,000”.

Then tell him to forget about the thousands and focus on the hundreds, then tens, etc.

Keep the 4 digit calculation easy. Avoid carries until he is comfortable working with 4 digits.

I think the above will catapult him into 4 digit calculations and boost his confidence.

Now I have a question for you.
What made you decide to teach the soroban and anzan to your son?

(Rose) #43

Thank you Kinma,

I am Japanese descendant and my Mom tried to teach me when I was a little kid but I was not interested. I wish I had stick to it.
I never thought I would have to learn soroban now that I am older, actually way older : ). I guess all started when my kid was 5 years old and he seemed to be a fast learner in Math, so I started looking for different resources and I found out about a school that teaches the abacus but not soroban. The guy did a bit of a demonstration and I was quite impressed with this kid that was doing this memory calculation at such early age. I didn’t enroll my son because the school is a bit far from where I live and the children have a 2 hour lesson. I thought it was too long for a 5 year old to be seating in a classroom. And also because they don’t use soroban, and they use both hands to make the calculations. It was a bit strange for me.
As I was familiar with Soroban, I decided to try and bought a little 5 digits soroban with big rods, got some books and stuff online and started learning myself, this was back in 2016. I found out that is possible to learn and teach my son. I just had forgotten how wonderful this ancient art was. I stopped for a while as it was hard to keep my son interested, now that is older I can make him sit for 10/15 minutes to practice soroban. I just hope I can discipline myself and continue learning.

#44

Modulo calculation on the soroban

Let’s do something more elaborate using an abacus or soroban.

Let’s do the 11 proof on a soroban.
Why? Because it allows us to check the correctness of the answer of any calculation.

Let’s first do this on paper, using just digits instead of beads to show the process.

If I take a number like 53, I can subtract 44 to get 9.
If I take a number like 535, I can subtract 440 to get 95. Then I can subtract 88 to end up with 7.
If I take a number like 5355, I can subtract 4400 to get 955. Then I can subtract 880 to end up with 75. Last I can subtract 66 to get 9.

Observe that with each step I lose one digit. In the last example I went from 4 digits (5355), to 3, to 2, and finally to 1.

Also observe that we only look at the 2 leftmost digits. In the case of 5355, we first only look at ‘53’. We subtract 44 to get 9. The other 2 digits are left untouched, so after that we regard ‘955’, again only look at the 2 leftmost digits or ‘95’, and subtract 88.

Thirdly observe that if the second digit is the same or higher as the first we can subtract 11 times the first digit, like in 23, we can subtract 22.
If the first digit is the higher as the second we can subtract 11 times the first digit minus one, like in 97, we can subtract 88.
In short; in al glance you can see the number to subtract.

On the soroban you can do the same.
If you see 5355 you now know you can take the modulo 11 in 4 easy steps.