Sometimes students see knowledge as something that generates grades, and feel that their partial knowledge should be rewarded accordingly. However, a lot of partial knowledge on many topics does not add up to real knowledge, and to learn for partial knowledge can eventually lead to a ``mathematical shut-down'' in understanding. A teacher naturally does not want to encourage learning for partial knowledge. What may seem to you a halfway answer would probably not be accepted in most careers in the real world where small errors could send an astronaut on the wrong orbit or produce other disasters. On a practical level, neater, more organized work will help you stay under control while working a problem. A teacher is more likely to assign partial credit if you appear to be in control of the problem, rather than flailing; and the way you present the mathematics on your test (do you work down the page or scribble all over?) may affect this perception more than you realize.