There is an exam. There are 25 exam question papers for 25 students who are lined up outside of the classroom. Each time, a students gets into the classroom, pick one paper (RANDOMLY) and go, sits on its desk and start his exam.
You are the 5th person in the line, who has to go to the class and pick a paper. Among those 25 papers, there is only 1 paper which questions are familiar to you.
Now the problem is: What is the probability that you will go into the classroom, and pick that one paper you want. (In other word, the probability that NO other student before you, will pick that exam paper which questions are familiar to you)
Thank you in advance.