What makes this idea so attractive to students? Why should it be true that 
Author: mpershan
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“27 – 11 = 38”
I love this mistake. From their work, what can we infer about what the student knows? Where are they getting confused? How would you help? (Also, if you don’t feel as if you have enough information, feel free to jump in with want information you’d like.)
Elementary teachers? You out there?
We here at the MathMistakes world headquarters got today’s mistake via email submission:
Question: If you are driving 60 km/h, how far would you go in 20 minutes?
Student’s answer: 1200 km
Since we don’t have much to work with, in terms of diagnosing the students’ error, let’s do two things in the comments today. First, leave a note if you have about the specific question and student answer. Second, let’s use the comments as a place to discuss strategies for helping students form an intuition for rates.
What is this student thinking? It’s a bit tricky, so extra points if you come up with a complete story that includes a list of things that we know that this kid knows.
Cena, wherever she is these days, deserves a medal. This video is a classic.
Here we get to see how the teacher followed up with the student, so let’s tackle these questions:
- What can we say that Cena does know?
- What is going through her head as she answers these questions? Where does she go wrong?
- What are the teacher’s moves in this clip? What is her strategy for uncovering the student’s errors?
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Call for submissions
Hey everybody,
One of the best ways to support this project is to submit some student work. We’ve got about another week worth of student work before we run out, so if you enjoy this site I’d like to encourage you to submit. A couple of things about submitting work to the site:
- Some people aren’t allowed to share original student work. You can still share, though, if you just copy or type out the student’s work. We’ll post that.
- Once school starts, I’m going to just have a camera with me every time that I grade. When I see something interesting or representative of a common error, I’m going to snap a quick picture of it. It would be great if a lot of you would do the same.
- I also post other sources of student errors. So if you’re watching a video on youtube, reading an article with some good samples of student thinking, or looking through the Q&A section of a Khan Academy video, feel free to submit those too. Really, anything that represents mathematical thought is fair game for the site.
Thank you for all of your support so far. Your submissions and comments are already making this site a really valuable tool for a lot of people. Great work, gang! Let’s keep it up.
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Tangent Lines
We’re putting together a nice collection of Calculus work. Keep up the great submissions!
What does this student know how to do? Given what the student knows, what’s your best guess as to the source of the error? How might you help?
From the student’s work, what can we infer that the student knows? What is the student thinking? How would you help?
This student has done a great job articulating their issue. How would you help?
What aspect of solving linear equations is this student struggling with? From the student’s point of view, why does the moves made seem like the right ones?
Are there any interesting things that you do to help students with linear equations? How do you make the right moves seem intuitive?