A friend of mine, an Oxford-educated mathematician, had a smart strategy to succeed in university. When two or more of her professors scheduled exams for the same week, she would immediately ask the instructors to clarify to what extent these exams would influence the final class grade. If the exam in one class was worth, say, 25 per cent of the final grade, and the exam in the other class was worth 50 per cent of the final grade, she would spend significantly more of her efforts studying for the second class.
This seems logical and self-evident.