Answer:
1/1560
Explanation:
The chance of you winning is 1/40, since there are 40 students and you are one of those students. Since, you cannot win again once you win once, you are eliminated. This leaves us with 39 people left. The chances of your friend being chosen out of the 39 people left is 1/39. Now you must multiply 1/40 and 1/39. After multiplying, you get 1/1560.