Students arrive at an average of 4 every hour to see the principal. The pricipal takes and average of 12mins per student.
(i) Calculate the amount of time the prinipal is idle
(ii)Determine how many students would be waiting to see the principal and how long they must wait
With the problem mentioning average twice, I assume this problem will be using averages. Thus. . .
Since an hour is 60 minutes, and students arrive on average 4 an hour, that means they arrice every 15 minutes. Since the principal takes 12 minuets per student, the principal sits idle for 3 minutes every minutes, or 12 minutes per hour, assuming he does sit idle at the same pace he sees students.
Then, for the second part, it seems like there is information possibly missing. For, on average, no student would have to be waiting, unless something like several students come all at once, if the students sits idle, etc. Feel free to message me if there is more information.
Good luck, Alex. I hope this helps.