Raddy, I'm not sure if this helps. Passing exams, doing math questions the way it's required (read carefully, write down workings logically etc) are skills that have to be learnt.
My son has this problem on and off. He usually writes the answers down without any workings, which is a real pain if he messes up and I try to go over with him on what went wrong. Many times, he wouldn't know how he arrived at the answer - I call it "blink math", where he blinks out the answer. It's great for speed but not for accuracy! I'm trying to get him to slow down and write down what's necessary - a working here or there will suffice.
My suggestion is to go through a few questions with him - the objective is for him to s-l-o-w-d-o-w-n and experience his own thought process. Focus on a few questions a day for several weeks if you can. I'm doing this with my son too - it's not easy because he hates to write (not even a bit), but I think it's helping him to understand his own thought processes and to have better accuracy as a result.
Good luck!
