In the course of the semester I give a total of 4 exams each of 5 problems
with at least 3 parts. I allow the students a double period (2hrs) to do this.
most of my students actually finish in about 1.5 hrs. I try to adjust the exam
problems not to be "tricky" but rather straight-forward, but definately
requiring more than just "plug-and-chug". As a test of fairness and
difficulty, I expect to be able to do the same test in 1/3 to 1/2 the time it
takes the students (or the bulk of them).