21 - Not 66.6%
In the opening scene, in the classroom at MIT, there are 3 blackboards with equations on them. The teacher asks the student which one is the correct formula. The student doesn't say anything until the teacher reveals one of the answers behind the board that are incorrect. The student then aswers. He states that with 3 blackboards, there was a 33.3 percent chance of success. But, with only two blackboards, his chances are 66.6 percent; the odds are in his favor. In REALITY, with only two blackboards left, his chances would only increase to 50/50.