Here's the question you clicked on:
julian25
3 individuals take the elevator in 15-story building. What are the odds they all will get off on the same floor? Notice: they are all strangers to one another.
I'd say it is like this: suppose they they leave the elevator one by one. For the first person, it doesn't matter where he or she leaves. For the second one, there is a 1/15 chance that he/she also leaves. The third one: also 1/15. To have them both leave at the same story: 1/15 * 1/15 = 1/225.