It's working fine except that I noticed that credit is being given to the students in an odd incremental way that depends on the number of answer blanks visible so far.
If I display one answer blank to start and they get that one correct, it displays the next step that contains an additional two answer blanks. This also gives the student 33% on the problem, although the first blank is really a very small step in the problem (stating the LCD). This makes some sense, because there are currently three answer blanks visible.
Then in the next step another answer blank appears and the student progresses to 75% on the problem (for three of the four answer blanks correct).
For the last step, the students have 80% on the problem from getting four of five answer blanks correct (progressing only 5% for the previous fairly important step). If they get the last step correct (giving the solution set, which is again not the major step in the problem), they earn the remaining 20%.
Is there a better way to cause the grade to be more evenly distributed?
I expect that perhaps a custom graded of some kind could be used, but will the parts that are not yet visible cause this graded trouble determining the correct percentage score to give?