Question

Use Johnson's rule to determine the optimal sequencing for the five jobs to be processed on two machines in a fixed order (Machine 1 before Machine 2). The processing times are given in the table below.

Job	Machine 1	Machine 2
L	10	2
M	5	4
N	7	5
O	3	6
P	1	7

** Please show excel steps so i can see if I did this right** thanks

1. What is the optimal sequence?

2. What is the total flow time for this sequence?

Answer 1

Answer

• What is the optimal sequence? - P , O , N , M L
• What is the total flow time for this sequence? - 26 hours

Pls. see the details below:

	Processing times
Job	Machine 1	Machine 2
L	10	2
M	5	4
N	7	5
O	3	6
P	1	7
look for the lowest time	1	=MIN(B3:C7)
	which is Job P Machine 1
Next step
Look for next min out of L M N O	2	=MIN(B3:C6)
	which is Job L Machine 2
	so we place it at the end as Machine 2
Next step
Look for next min out of M N O	3	=MIN(B4:C6)
	which is Job O Machine 1
	so place at the 2nd position
Next step
Look for next min out of M N	4
	which is Job M Machine 2
	so placed at 2nd last position
Optimal sequence is
P,O,N, M,L

Optimal Sequence
P	O	N	M	L

• Total flow time of the sequence is 26 hours as I have placed the optimal sequence in order in an excel and job L finally end at Machine 1 at 26 hours

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26
Machine 1	P	O			N							M					L
Machine 2		P							O						N					M				L

Excel

If you liked my answer thumbs up pls.