DH was (and still is) like that...figuring all in his head before writing anything down. Says he used to get scolded by the teachers all the time for not writing the formulas - just the answers. And being the person he is, would argue with the teacher that since the answer was correct, why was it such an issue not writing the formula???? He is my go-to guy when it comes to fabric calculations! Cuz I just absolutely suck at math.