Anon,I don't believe that doing an A-Level course is a relevant way to prepare yourself for the numerical element of MC interviews. If you feel you generally have a weakness in that area, fine. But if you simply want to be a bit more nimble with mental arithmetic to get by interview, then re-learning things like Integration will get you nowhere.There are probably a short list of key calculations you need to be comfortable with for MC interviews. List them, and just develop fool-proof methodologies you will remember. I propose a few below, perhaps others can chip in also.- Formulae for the caluclation of volumes of basic shapes. In case you're asked one of those "how many golf balls fit inside... whatever".- converting fractions to percentages. For tackling mkt sizing Qs, for example. i.e. calculate # of ppl in a target age group of a given population.- applying %s to numbers. i.e. caluclate 7% of 250.- practise dealing with numbers in the millions/billions, so as not to get lost in zeros- then you're just left with your bread & butter stuff: + - * /