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1. You have just taken control of the scheduling divison of your company. In the

ID: 461296 • Letter: 1

Question

1. You have just taken control of the scheduling divison of your company. In the next week you have 6 jobs that need to be completed (see the table below). Your boss has asked you to analyze two methods to determine the best way to schedule. Todays date is 100

a) Schedule the jobs according to SPT, and give the average lateness and average completion time using SPT. (Round to two decimals)

b) Schedule the jobs according to CR, and give the average lateness and average completion time using CR. (Round to two decimals)

Jobs` Process Time (days) Due Date A 4 160 B 12 125 C 9 138 D 20 137 E 2 150 F 15 120

Explanation / Answer

a) SPT is Shortest Processing Time scheduling. It sequences the jobs based on least to highest processing times

Current date is 100. Hence effective due dates will be Due date - 100

Average Lateness = 49/6 = 8.17 days

Average Completion Time = Total Flow Time/6 = 154/6 = 25.67 days

b) CR is Critical Ratio method of scheduling. It is the ratio of processing time of the job and remaining time until due date.

Average Lateness = 52/6= 8.67 days

Average Completion Time = Total Flow Time/6 = 275/6 = 45.83 days

Jobs Process Time (days) Flow time (cumulative) Due Date (Due date given - 100) Lateness E 2 2 50 0 A 4 6 60 0 C 9 15 38 0 B 12 27 25 2 F 15 42 20 22 D 20 62 37 25