Question

The following jobs are waiting to be processed at Jeremy​ LaMontagne's machine center. Today is day 240.

Job	Date job received	Due date	Duration (days)
1	210	270	25
2	215	280	35
3	220	295	45
4	235	315	40
5	240	340	15

Calculate the Critical Ratios​ (CR): ​(Enter all responses rounded to two decimal​ places.)

JOB     CR

1         ?

2         ?

3         ?

4         ?

5         ?

Using the Critical Ratio (CR) scheduling rule for sequencing the jobs, the order is:

Sequence       Job

1                       ?

2                        ?

3                        ?

4                        ?

5                        ?

Answer 1

Answer (i)
Critical ratio is defined as the ratio obtained by dividing the time remaining for due date by the total machine time left for that job.
Critical ratio (CR)= Time remaining before due date/Remaining processing time
Therefore for the given data, the CR will be:

Job	Date job received	Due date	Duration (Days)	Days left to due date (Due date-240)	CR (Days left to due/Duration)
1	210	270	25	30	1.20
2	215	280	35	40	1.14
3	220	295	45	55	1.22
4	235	315	40	75	1.88
5	240	340	15	100	6.67

Answer (ii)

For scheduling the jobs, just arrange the jobs in the increasing order of their CR.

Job	Date job received	Due date	Duration (Days)	Days left to due date (Due date-240)	CR (Days left to due/Duration)	correct Order for scheduling
1	210	270	25	30	1.20	2
2	215	280	35	40	1.14	1
3	220	295	45	55	1.22	3
4	235	315	40	75	1.88	4
5	240	340	15	100	6.67	5

Therefore, the correct order will be  
2 -> 1 -> 3 -> 4 -> 5

Dear Student,
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