Question

Question 45 Unsaved A professor holds office hours during final exam week and discovers much to his dismay that his sudden popularity affords him little time to engage in his favorite activity, watching cat videos. Fifteen students per hour arrive at his office and he patiently answers questions, averaging three minutes per student. If the average cat video is 60 seconds, how many videos can the professor watch in an hour? A. 20 B. 18 C. 15 D. 24

Answer 1

? =mean arrival rate of customers = 15

? = mean service rate

He take 3 minutes to answer 1 student

so in 1 hour,he can serve 60/3 =20 students

so mean service rate = ? =20

the average utilization of the system,p =?/? =15/20 =0.75

so 1-0.75 =0.25 =25%

so he is free for 25% of time

so 25% of 1 hour =25% of 60 minutes =0.25*60 =15 minutes

That means in an hour, professor is free for 15 minutes

the average cat video is 60 seconds that is 1 minute

so in 15 minutes,number of videos he can watch =15/1 =15

Hence,answer is choice C 15