You attend a multiple choice question exam, and you have n (say 10) questions whose answers you don't know at all. There are 4 choices in each question. A correct answer yeilds 1 marks. An incorrect answer has penalty of -0.25 marks. Is it wise to attempt all the questions in random? It seems wise to me. What if n = 3 (or 1). There are thousands of student participating (no-one knows the answers . You have to stand above maximum of them.