There are no mistakes.

[Nicholas]

I was just watching this short video on decision making and it reminded me of my experience in maths exams. It was more important to show the working out of an answer than it was to arrive at a correct answer. Having said that I got a point for a correct answer and a point for the correct method, so the marking system did not highlight the importance of mindful working over resulting conclusion.

Rabbi Dr. Abraham Twerski explains it much better than me