A machine shop has two machines, A and B. Four jobs need to be processed through machine A first and B second. Job 1 will take one hour on machine A and three hours on machine B. Job 2 will take three hours on A and two hours on B. Job 3, seven on A and three on B. Job 4, five hours on A and one hour on B. Using Johnson's rule, in what order should these jobs be done?

Question

Fill in the blank(s) with the appropriate word(s).

Answer 1

1-3-2-4

Johnson's rule states:

1. List the operation time for each job on both machines. 2. Select the shortest operation time. 3. If the shortest time is for the first machine, do the job first; if it is for the second machine, do the job last. In the case of a tie, do the job on the first machine. 4. Repeat Steps 2 and 3 for each remaining job until the schedule is complete. The shortest operation is for job 1 on machine A, so we will do that job first. The shortest job for machine B is job 4, so we will do that one last. The next shortest job is two hours on machine B for job 2, so we will do that next-to-last. The resulting schedule is 1, 3, 2, and 4.