When subtracting a mixed number from a whole number, the whole number should first be converted to a mixed number, e.g. 8 – (2+2/3) = (7+3/3) – (2+2/3) = 5+1/3. The student incorrectly believes that a whole number should be converted to a mixed number before adding it to a mixed number.

“The student incorrectly believes that a whole number should be converted to a mixed number before adding it to a mixed number.”

It may not be necessary but there is nothing wrong with this strategy, and it would have worked fine if the student hadn’t turned 8 into 8 and 3/3.

Andy “SuperFly” Rundquist

I guess my question is: What sort of feedback would have worked best for this student? As secretseasons points out, there seems to be only one tiny mistake here (8 != 8+3/3), otherwise the students seems to understand what’s going on. However, since it’s adding, as Dave says, they didn’t really need to break up the “8” after all. Clearly if you talk with the student, you could figure this out. But what could you put on the page (besides the “X”) to get them to learn?