Thanks to a generous and eccentric donor, the school of business has 3 fax machines.The toner in each machine needs to be changed after about 5 hours of use.There is one unit secretary who is responsible for the fax machine maintenance.It takes him 15 minutes to replace the toner cartridge.What is the average waiting time in the queue?
A).0142 hour
B).1563 hour
C).0249 hour
D).2749 hour

Question

Quizplus · Accepted Answer

Since there are 3 fax machines, and each toner cartridge needs to be changed after 5 hours of use, that means the unit secretary will need to change the toner on each machine once every 5 hours. Therefore, the average time between each toner replacement is 5/3 = 1.67 hours. 
Since it takes him 15 minutes (0.25 hours) to replace the toner cartridge, the average waiting time in the queue is simply half of that, or 0.125 hours. 
Therefore, the answer is C), which is equal to 0.125 hours, or about 7.5 minutes.

Thanks to a Generous and Eccentric Donor, the School of Business