I'm not gonna say you gotta change career plans or anything, but mental math is a very good skill to have as an AA. Yeah as you're sitting there during a long case you can calculate fluid deficits/blood loss/etc with a calculator if you wish, but lets say you just mask induced a 3 yr old and they laryngospasm, there's not time to grab a pen and paper and figure out the IM dose of succ you need to give ASAP. If this is something you really struggle with you need to practice and make sure you are prepared before hand for any situation that might require quick calculations. I know one girl who worked at a peds hospital and she wrote out emergency drug doses based on each childs weight before the case. So there are ways around it, but don't kid yourself, its definitely useful to be good at mental math.