This two-minute video shows how to multiply 21 x 13, and 123 x 321, with an easy line-drawing and angle-counting method. No times tables needed!
Here is another very clear example showing 432 x 312, done with the same method. However it shows a way to “carry” digits.
Seeing these videos makes me wonder anew whether math is really about “shapes,” and about describing all the “shapes” in the universe.
If there is anyone from China reading this blog, I’d really appreciate knowing how extensively this method is actually used in schools.
–Eileen
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