What about this table and her knowledge about numbers, lead this kid to put down 39? Tell a story in the comments.
Author: mpershan
There were two parts to this calculus problem, and both parts are below. Time to sharpen your Calc skills, folks:
Calculus pros: what’s going on here? Where did the student go right? Where did she go wrong? How would you help?
How did this student end up with the answer he did? What does it seem that he knows about complex numbers?
I’m sitting on a bunch of Khan Academy questions from users that I marked as very interesting. I never posted them, and I feel a little cheap giving them all their own posts. So I figured I’d just dump the whole lot on you all. These questions reveal interesting things about the way these students are thinking. If you think that you’ve got something interesting to add, either on the diagnosis or prescription side of things, dig into the comments below.
The first is a nice probability puzzler. How did this student get 3/8?
I love this conceptual question.
Not sure exactly why I clipped the first question here, but the second question is great. “Why do they call it a limit?”
A good reminder: some vocab is tricky. Why are these two vocabulary words the one that this student confused?
This is a great point from a kid about variable use.
A little bit of context for this next one: we’re talking about protractors here.
What’s the mistake, and how would you move this student forward to a complete understanding of how to solve inequalities?
I usually try to at least come up with an idea of what the student was thinking before I post these mistakes on the site. Sometimes, though, I’m totally stumped. Here’s one that got me:
How did the kid get that answer? Anybody?
Also, how would you help the student move forward?
This student knows stuff. What does the student know? Where did they go wrong, and why do you think they went wrong? How might you help?
Here’s a conceptual question (taken from the Shell Centre) that provoked some solid responses from students:
Here are a few of the responses:
Categories
Adding Complex Numbers
What is it about complex numbers that this student finds confusing? Do you think he would make an identical mistake on 
Categories
Call for feedback: Categories
Hey everyone. The way that I’m categorizing mistakes isn’t really working for me, and I’m curious what all you users of the site think about what we’ve been doing.
Here are my questions:
- Suppose that I stopped categorizing posts by CCSS standard (i.e. “A.REI.3”) and instead used the CCSS categories (i.e. “High School – Algebra – Reasoning about equations and inequalities”). Would that bug you? Anybody out there really like the categorizing by standard?
- Right now I categorize posts in two different ways. First, by topic and course (i.e. “Algebra 1, Inequalities”) and also by CCSS. Let’s say that I told you that I was going to just do the CCSS stuff. Would that make you happy/sad/morose/nonplussed, or would that have no impact in your life?
I’m looking for feedback. Please leave a few quick thoughts in the comments of this post.
(Also, feel free to start a more general conversation about features of the site.)