Question

You have the following information on four jobs. Today is the beginning of day 1, so you can assume that the Time needed = work remaining and Due (days) = time remaining.

Job	Time Needed (days)	Due (days)
P	8	8
Q	10	23
R	3	17
S	6	30
T	4	29
U	7	24

1. If you order these jobs by Shortest Process Time rule, the order will be:

2. If you order these jobs by Earliest Due Date rule, the order will be:

3. What is the Average Flow Time if the jobs are scheduled using the Shortest Processing Time rule:

Answer 1

1) Scheduling by Shortest Processing Time (SPT) rule, the order will be in the ascending order of Time needed.

The order will be: R-T-S-U-P-Q

2) Scheduling by Earliest Due Date (EDD) rule, the order will be in the ascending order of Due time.

The order will be: P-R-Q-U-T-S

3)

Job	Time Needed (days)	Due (days)	Flow Time
R	3	17	3
T	4	29	7
S	6	30	13
U	7	24	20
P	8	8	28
Q	10	23	38

Flow time = Time needed for previous job + Time needed for current job

Average flow time = (3+7+13+20+28+38)/6 = 109/6 = 18.17 days