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Matrix multiplication *October 24, 2012*

*Posted by mareserinitatis in math, older son, teaching.*

Tags: math, matrix, older son

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Tags: math, matrix, older son

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The older boy was working on matrix multiplication in math. He got very testy with me: “Why do I even need to know this?” I replied that it’s used all the time in calculus-based physics. That disappointed him as he would like to take it some day.

He was super frustrated because the explanation on the computer was very…verbal. Unfortunately, I couldn’t locate my favorite linear algebra book, so I tried to go through and explain it while making some diagrams.

He still had some problems and then kept asking if they were somehow related to Punnet squares. Um…not really.

And then he made this diagram.

I have to admit that it’s not how I would think to multiply matrices…or at least I think there are easier representations. (In my mind, at least.) However, this did work in that it made sense to him, and once he had figured out enough to draw this, he was able to finish the rest of the problems on this concept.

This just goes to show that we don’t all think the same way, I suppose. The way we think about things may not always be the easiest for someone else.

See, it really does show the differences in thought processes. I don’t remember much about matrix multiplication, but looking at this diagram makes absolutely no sense to me. However, I’m willing to bet that if older boy explained this to my teenager using this diagram, my boy would understand perfectly. Meanwhile I’d still be scratching my head.

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I remember my maths teacher from high school explaining this by waving his arms:

– left arm goes left to right

and at the same time

– right arm goes from up to down.

And you do this for each row in the first matrix and each column in the second matrix.

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Hehe, I guess it makes more sense in my head.

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