If you're thinking of taking maths, remember, that if you study say, geography, or history, or whatever, you have **** loads of reading to do, but once you do all that, you cant fail an exam. How well above a pass you get depends on how you analyse the info they give you and how present your answers and ideas. In certain maths modules, maybe not first year ones, there is not much that you actually need to know. you can know all the theorems and lemmas, and even understand the answers to examples, but then have no idea how to do anything yourself.
However, that makes it way more fun!