A few days ago, I stumbled upon this article. The penmanship is fascinating, and those boards must have been covered up right around Thanksgiving! But my favorite picture from the article was the number wheel, which "apparently was used to teach multiplication tables." I've recreated it on our chalkboard to get a better look at it.

I realized that I've studied the differences in mathematics across thousands of years. I gave a discussion about the Babylonian number system recently, and a discussion on Ancient Chinese numerals is coming soon. But the fact that math can change so much in 100 years that I don't immediately understand this multiplication wheel is incredible!

In fact, I can't figure it out. While I drew the wheel out on our chalkboard, some other Center of Math staff members looked on- one suggestion involved Base 13, another suggested that it's similar to a clock. I finally found this Reddit thread about the original article. The theory that makes the most sense to me is that this wheel was used as a teaching tool; the teacher would point at a number in the center and then a number on the outside, asking a student to say the product. This is supported by the numbers on the outside of the ring. There are 4 sevens, whose products are commonly difficult for children to memorize. And there are no tens to be found, which are extremely easy to multiply.

A math technique developed between my sister and me |

So, to our readers, I'm curious. What math techniques did you learn as children that are outdated today? Do you prefer a new method that you've, perhaps, seen your children working on? Let me know what you think in the comments section!

I'll go first. I'm only four years older than my sister. But a few years ago, I was helping her out with some math- and there was something called the box method (used for factoring) that I had never seen before. I realized I had no idea how to help her without learning the new technique myself.

-Tori

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