What’s the mistake? Why did the student make this mistake, in particular?

Thanks again to the tweeting and blogging Kate Nowak for this submission.

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- Post author By mpershan
- Post date November 12, 2012
- 3 Comments on Perpendicular(?) Vectors

## 3 replies on “Perpendicular(?) Vectors”

The Student has confused collinear and perpendicular. I wonder if finding multiple values for t set off any alarm bells for the student?

My guess is that they are using a rote procedure (the wrong procedure) with no thought. I suspect that they could hold pencils in the air to demonstrate collinear and perpendicular vectors, but they are not thinking that way as they do the problem. Like most students, they did not think about their answer after they finished the procedure.

I really like most of Kate’s stuff, but I don’t like this problem. It just seems like a completely contrived attempt to dump a quadratic equation question into a vector unit.

Feedback on the quality of questions is always appreciated, I’m sure. But we should be just as cautious of being harsh when talking about the work of other teachers as we are when talking to our students about their own work.