A proctologist gets sick of his medical career and decides it's time for a change. He does a bit of research and settles on trying his hand at being a mechanic. He attends mechanic school diligently and pays attention in the hopes of being the best mechanic in town.

After taking his final exam, he notices a mistake with the grade on the test and asks the teacher.

"Sir, you have me 150% out of a possible 100% on the practical exam. This must be a mistake!"

The teacher replies, "It's no mistake. 50% of the grade is for perfect disassembly of the engine. 50% is for perfect reassembly of the engine. I gave you another 50% on top because you did it all through the exhaust pipe!"