I am almost certain that Ballmer did not take Math 55, though Bill Gates did (and supposedly got a ‘B’). Do you have a source citation for that? You don’t have to take Math 55 (a freshman course with 10–20 students per year) to graduate with high honors in Math/Economics. (Which isn’t to say that Ballmer is a slouch: he is clearly very sharp, and was even as an undergraduate.)