Answer:
21 minutes
Step-by-step explanation:
Her expected commute time is given by the probability of having to wait for the train (0.2) multiplied by the commute time in this scenario (25 min), added to the probability of not having to wait for the train (1 - 0.2) multiplied by the commute time in this scenario (20 min). The expected commute time is:
[tex]E(X) = 0.2*25+(1-0.2)*20\\E(X) = 21\ minutes[/tex]
Her expected commute time is 21 minutes.
