I started with this handout and a warm up problem of multiplying matrices (I had a diagram handy for students who forgot how to multiply matrices).

It didn’t go well at all. Can you help solve my matrix mess?

The problem was, I didn’t want to take the time to properly review matrices, I just wanted to remind students that they’re useful when solving systems. This obviously backfired.

You already know this is going to go badly because the material is split into three places and is dependent on me showing up with a diagram at the right moment. Students were totally baffled why they were multiplying matrices. They didn’t understand that the calculator would be taking the inverse (some tried to multiply the matrix by -1). They didn’t read the instructions all the way through and were calling me over to help with the calculator.

Head on over to the original post to get the whole story and see my attempt at a re-write. Thoughts on how to salvage this lesson would be greatly appreciated!