Metro trains in Manhattan arrive at your train station exactly every 15 minutes (i.e., the times between arrivals are 15, 15, 15, and 15 in an hour). If you just arrived at the train station at a random time, what is the probability that the next train will arrive within 5 minutes?
If you arrived at the train station at a random time and have waited for 5 minutes, what is the probability that the next train will arrive within 5 minutes?
If you arrived at the train station at a random time and have waited for 5 minutes, how much more time, on average, do you have to wait for the next train?