I’m inclined to say that this is a classic working memory mistake. You’ve got a resources-heavy calculation being done in the student’s head, and you’ve got this 3 floating around in the problem, and it ends up in the ones place.

Agree? Disagree? Thoughts?

  • Michael Paul Goldenberg

    For the old blind bats in the room (or bat, if I’m alone): it’s challenging to see these last few scans with the heavy shadows. Also, what grade are the students?

    That said: I would want to watch the student or have her/him do some similar problems and see if this is a fairly frequent error, and if it is dependent upon certain number combinations or fairly random. Your speculation might be right, but based on this single example, it’s hard to say.

    • Yeah, sorry about the scans. Using my new iThing is convenient, but images aren’t coming out so well. I’ll revert back to my old clunker of a camera. And these are 4th graders, on the first day of school.