7 pages of replies have made me reminisce about my classes quite a bit. I identify with a lot of you who commented that the math profs often didn't speak English. Isn't the subject hard enough??? Thinking about all the difficulty classes makes me realize that if I had to go back to school again and start from freshman year, there is no way I'd make it through to graduation!!!
As for the hardest class I've ever taken, it was probably graduate level electrochemistry. I missed the first day of class and never understood anything during the lectures. I didn't understand anything in the book, either. This class, more than any other, made me want to drop out of school. Prof gave me a huge gift by giving me a C or D or whatever my grade was.
I would have been happy to have escaped having to repeat the class except that my focus in grad school was electrochemistry of semiconductor surfaces. I graduated but never understood the math behind it all. Needless to say, I am no longer a chemist!!!