A philosophy professor walks in to give his class their final. Placing his chair on his desk the professor instructs the class, "Using every applicable thing you've learned in this course, prove to me that this chair DOES NOT EXIST."
So, pencils are writing and erasers are erasing, students are preparing to embark on novels proving that this chair doesn't exist, except for one student. He spends thirty seconds writing his answer, then turns his final in to the astonishment of his peers.
Time goes by, and the day comes when all the students get their final grades ... and to the amazment of the class, the student who wrote for thirty seconds gets the highest grade in the class.
At Sydney University, there were four students taking Organic Chemistry. They did so well on all the quizzes, midterms and labs, etc., that each had an "A" so far for the semester. These four friends were so confident with the finals approaching that the weekend before, they decided to go down to Canberra and party with some friends there.
They had a great time. However, after all the hard partying, they slept all day Sunday and didn't make it back to Sydney until early Monday morning - the morning of their final exam! Rather than taking the final then, they decided to find their professor after the exam and explain to him why they missed it.
They explained that they had gone to Canberra to do some research in the ANU (Australian National University) archives for the weekend with the plan to come back in time to study, but, unfortunately, they had a flat tire on the way back, didn't have a spare, and couldn't get help for a long time. As a result, they only just arrived now!
The professor thought it over and then agreed they could make up their final exam the following day. The guys were elated and relieved. They studied hard that night - all night - and went in the next day at the time the professor had told them.
He placed them in separate rooms and handed each of them a test booklet, (which was out of 100 points) and told them to begin. The first problem was worth five points. It was something simple about free radical formation. Cool, they all thought in their separate rooms, "this is going to be easy."
Each finished the problem and then turned the page. Question 2 (for 95 points): Which tire?