Question

2 CADT organize the entrance exam for the new academic year. The exam is of the multiple-choice question form. For each question, there exists 4 choices and among which one is correct. Condition of the exam is: if a student chooses the right answer, he will get 3 points, otherwise he will lose 1 point. Question: if a student decides to answer a question, how many points does he expect to gain/lose?

Answer 1

In an entrance test, there are multiple choice questions. There are four possible answers to each question, of which one is correct. The probability that a student knows the answer to a question is 90%. If the gets the correct answer to a question, then find the probability that he was guessing