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# Johnson's rule - Rank the Critical ratio sequencing rules

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Rank the Critical ratio sequencing rules on the three evaluation criteria of average flow time, average number of jobs in the system, and average job lateness for the information below. (Do not evaluate shortest processing time or first-come first-served).

A production planner must decide the sequence in which to produce four customer orders.

Customer
Order Estimated Production Time
(days) Time to Promised Delivery (days) First-Come
First-Served
Order Sequence Flow- Time
(days) Lateness
(days)
A 10 15 1 10 0
B 21 30 2 31 1
C 26 60 3 57 0
D 19 77 4 76 1

Problem 2:

Develop a job sequence for the five jobs with the information given below.

Jobs that Precede

A B C D E

A 55 41 64 50 B 63 51 46 62
C 42 48 49 40
D 43 61 55 57
E 59 67 47 53

a. Determine job sequence

ilb. What is the total change over cost for all five jobs?

Problem 3:

A production planner must determine the sequence to process 6 customer orders. Each of the orders must go through two principal operations. The following time estimates for the four orders are:

Orders 1st operation 2nd operation

A 1.2 1.9
B 1.5 1.0
C 1.7 1.3
D .8 1.5
E 1.4 .9
F 1.2 1.2

a. Use Johnson's rule to set the sequence of processing the shipments.

b. How much total time is required to process the six shipments through both operations?

Hint. If times are tied in first and second operation, always select the first operation. If times are tied in either the first or second operation between two tasks, then go to the second operation/first operation to decide between the two.

#### Solution Summary

This provides an example of using Johnson's rule to set a sequence for processing shipments in a scheduling problem.

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