Use the scenario given below to answer the following question(s).
You arrive at a queue and spend 10 minutes in the system (waiting plus service).During this time,customers arrive at the rate of 15 per minute.The mean service rate is 20 per minute.
-Assuming Little's law,determine the number of customers that remain in the system when you leave.
A)250
B)25
C)150
D)100

Question

Quizplus · Accepted Answer

Little's law states that the long-term average number of customers in a stable system is equal to the long-term average effective arrival rate multiplied by the average time a customer spends in the system. 
In this scenario, the effective arrival rate is 15 customers per minute and the average time a customer spends in the system is 10 minutes. Therefore, the average number of customers in the system is:
15 customers/minute * 10 minutes = 150 customers 
Since you are one of the customers who spent 10 minutes in the system, the number of customers who remain in the system when you leave is:
150 customers - 1 customer (you) = 149 customers 
Therefore, the best choice is C, 150.

Use the Scenario Given Below to Answer the Following Question(s)