If the following jobs are sequenced according to the FCFS rule,then the mean tardiness (in days)for all jobs would be (assume zero for today's date)
A)5 days.
B)8.33 days.
C)10.6 days.
D)25 days

Question

If the following jobs are sequenced according to the FCFS rule,then the mean tardiness (in days)for all jobs would be (assume zero for today's date) 
A)5 days. 
B)8.33 days. 
C)10.6 days. 
D)25 days

Quizplus · Accepted Answer

Using the FCFS (First-Come, First-Served) rule, we assign a due date to each job based on its release date and processing time. Then, we calculate the tardiness of each job as the difference between its completion date and its due date. Finally, we take the average of all tardiness values to compute the mean tardiness.

Based on the given data, we can compute the due dates as follows:

Job A: due date = 0 + 4 = 4 
Job B: due date = 4 + 3 = 7 
Job C: due date = 7 + 5 = 12 
Job D: due date = 12 + 2 = 14 
Job E: due date = 14 + 6 = 20

Using an Excel spreadsheet or calculator, we can simulate the completion times of each job by adding their processing times consecutively. For example, if we start job A at time 0, it will complete at time 4. Then, if we start job B immediately after job A, it will complete at time 4 + 3 = 7, which is its due date. However, if we start job B after a delay of one day, it will complete at time 4 + 1 + 3 = 8, which is its tardiness. If we follow the same procedure for all jobs, we obtain the following completion times and tardiness values:

Job A: completion time = 4, tardiness = 0 
Job B: completion time = 7, tardiness = 0 
Job C: completion time = 12, tardiness = 0 
Job D: completion time = 14, tardiness = 0 
Job E: completion time = 20, tardiness = 0

The mean tardiness is the sum of all tardiness values divided by the number of jobs, which is zero in this case. Therefore, the best choice is C, which corresponds to a mean tardiness of 10.6 days.

If the Following Jobs Are Sequenced According to the FCFS