## Sunday, September 22, 2013

### Matrices ... how to teach the nitty gritty

I'm working on lesson plans for our next unit ... which is on Matrices.  In past years students have only been taught how to solve them on their calculators.  I'm glad we are going to teach them a bit more ... how to add, subtract, multiply by a scalar, and multiply matrices.  Then we have been asked to teach them how to solve a system (2 x 2 only) using matrices ... using the determinant and inverse.

Here is my plan.  I'd love to hear your thoughts ... trying to make what seems to be difficult and obtuse concepts real for my students.  I don't usually use fill in the blank notes but this time around they seemed useful.

We are starting with an Oreo question ... in hopes to soothe (smooth) the path to the work.

1. I had my husband do the oreo problem and I am glad I did. He did it kind of using ratios. If 3 cookies have 160 cal then 1 cookie has about 53 cal and if 2 cookies have 140 cal then 1 cookie has 70 cal, so the extra filling must be 17 cal. Then, the regular cookie is 57 -13=44/2 wafers so 22. Just keep in mind they can do it this way. Half of my class did it this way, half thought of systems.

1. Thanks for the heads up ... it will make for an interesting discussion if students use ratios. I think my next question will be ... will ratios work on most systems problems?

2. When I tackled the oreo problem last year some other interesting questions came up. We used Christopher Danielson's information and started asking whether the golden wafers and the regular wafers had the same calorie and fat contents. We asked whether the double deckers had the same wafer in the middle as on the outside. Some really great conversations...

3. Thank you ... will bring in some of the other Oreo products ... looking forward to the discussion!

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