Question

Part 5.   Questions 8,9. [ Use Video-1 under Scheduling heading. ]

[Note: The order of jobs in a schedule is 1^st,2^nd,3^rd, for A,B,C, respectively.]

Consider the jobs scheduled on two machines in the order of (A,B,C) where each job is started as soon as possible. The processing times for each job on each machine are given in the table below. Assume time on machine #1 is represented with “(1)” and on machine #2 with “(2)”.

Job	Machine#1 Time	Machine#2 Time
A	2	1
B	3	2
C	1	3

Question 8. Which Gantt chart is correct for the schedule (A,B,C)?

Gantt Chart A	Job	T1	T2	1	2	3	4	5	6	7	8	9	10	11	12
	A	2	1	(1)	(1)	(2)
	B	3	2			(1)	(1)	(1)	(2)	(2)
	C	1	3						(1)		(2)	(2)	(2)
Gantt Chart B	Job	T1	T2	1	2	3	4	5	6	7	8	9	10	11	12
	A	2	1	(1)	(1)	(2)
	B	3	2			(1)	(1)	(1)	(2)	(2)
	C	1	3						(1)	(2)	(2)	(2)
Gantt Chart C	Job	T1	T2	1	2	3	4	5	6	7	8	9	10	11	12
	A	2	1	(1)	(1)	(2)
	B	3	2			(1)	(1)	(1)		(2)	(2)
	C	1	3						(1)			(2)	(2)	(2)
Gantt Chart D	Job	T1	T2	1	2	3	4	5	6	7	8	9	10	11	12
	A	2	1	(1)	(1)	(2)
	B	3	2			(1)	(1)	(1)		(2)	(2)
	C	1	3						(1)	(2)	(2)	(2)
E	E. None of the above

. . .

Question 9. How many of the statements are correct for the schedule (A,B,C)?

     (A) 0   (B) 1   (C) 2   (D) 3   (E) 4

Statement 1. The total processing time of the schedule is 10

Statement 2. The total queue time of job C is 6

Statement 3. The total flow time of job B is 7

Statement 4. The total idle time of machine 2 is 4

. . .

Answer 1

Question – 8:

Answer is: Gantt Chart A

Explanation:

As the sequence is A, then B and then C:

Machine 1 will start with A and will process for 2 time period

Then Job A will be processed in Machine 2 for 1 time period

Now as after t-2, Machine 1 is free, B can start from then for 3 time period

And so on.

Hence.

Question – 9:

From the gantt chart A provided in que-8:

Statement 1 is true as the total time is 10

Statement 2 is true, as total queue time is 6 (5 to start and then 1 to wait for Job B to finish from Machine 2)

Statement 3 is true as total flow time is 7 (from the starting of Job A, till the end of Job B)

Statement 4 is also true. (Machine 2 is idle for time 1, 2, 4, 5, and 7.

Answer is: (E) 4

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