Question

Jack, the owner of Jack's Electronic Repair, currently has five jobs to be scheduled, shown in order in which they arrived:

Job Processing Time (h) Due (h)
V 3 5
W 1 1
X 4 9
Y 2 3
Z 5 7

If Jack uses the shortest processing time first (SPT) priority rule to schedule these jobs, what will be the average flow time?

A) 8 hours
B) 5 hours
C) 7 hours
D) 7.2 hours
E) 3 hours

Answer 1

The average flow time using the shortest processing time first (SPT) priority rule is 7.2 hours.

Step-by-step explanation:

To calculate the average flow time using the shortest processing time first (SPT) priority rule, we need to determine the completion time for each job and then find the average.

Using the SPT rule, we start with the job that has the shortest processing time, which is Job W with 1 hour. So, Job W will be completed at time 1.

Next, we move to the next shortest processing time job, which is Job Y with 2 hours. So, Job Y will be completed at time 3 (1 + 2 = 3).

We continue this process for the remaining jobs, and we find that the completion times for the jobs are: Job W - 1 hour, Job Y - 3 hours, Job X - 7 hours, Job V - 10 hours, and Job Z - 15 hours.

To calculate the average flow time, we sum up the completion times for all the jobs and divide by the total number of jobs. In this case, the average flow time is (1 + 3 + 7 + 10 + 15) / 5 = 7.2 hours.

Therefore, the correct answer is D) 7.2 hours.