The January 2017 New York regents exam in Algebra I (Common Core) contains a question with a model response that I do not get.
Here are the directions:
Here is the question and the model response:
The student has shown in 2 steps how to convert one equation into slope-intercept form, and you can see that the equation ends up identical to the first equation in the question. In answer to "Is he correct?" the student answers "No." In explanation, he states that the two equations are for the same line.
The model response scoring states: Score 1: The student wrote an incomplete explanation.
Mathematically, this model response nailed it. For some reason it only gets half credit. Was it not verbose enough? Is there a minimum number of words required?
You can see the entire group of model responses here.