This Japanese Multiplication Method Will Divide Your Brain By Zero

When I first saw this Japanese multiplication method, I just couldn't believe it. Then I tried it and it works perfectly, but still can't understand how it works—or how anyone found this method.

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You just need to follow the instructions in the video, and you will be able to multiply any number by any number by just counting the dots in the grid.

DISCUSSION

bustedchain
bustedchain

I guess for this to work you have to take any column that is greater than 9 and carry the tens digit back up to the higher column. Then, if that column becomes greater than 9 you have to carry that tens up to the next column.

This wasn't automatically clear to me until I ran through 123x456 and figured out that to get the right answer I had to really figure out what was going on with the carried digit.

I'm sure lots of other people figured that out on their own...takes me a minute.