A professor was marking some exam papers and opened one from a failing student to reveal blank pages and a £100 note. The only thing written on the answer page was, "£100 = 100% - I get a distinction."
A month later, the student approached the professor. "I don't understand," he said. "I failed the course! Didn't you read my paper?" The professor handed the exam paper back to the student.
The student opened it to reveal £50 and the phrase "£50 = 50% - You fail!"