Question
Processing times (including setup times) and due dates for six jobs waiting to be processed at a work centre are given in the table. The average tardiness (in days) using shortest processing time rule is ___________ (correct to two decimal places).
| Job | Processing time (days) |
Due date (days) |
| A | 3 | 8 |
| B | 7 | 16 |
| C | 4 | 4 |
| D | 9 | 18 |
| E | 5 | 17 |
| F | 13 | 19 |
Answer :
6.33
By STP rule
| Job | PT | DD | Job FlowTime |
Tardiness |
| A | 3 | 8 | 0+3 = 3 | 0 |
| B | 4 | 4 | 3+4= 7 |
3 |
| C | 5 | 17 | 7+5 = 12 | 0 |
| D | 7 | 16 | 12+7 = 19 | 3 |
| E | 9 | 18 | 19+9 = 28 | 10 |
| F | 13 | 19 | 28+13 = 41 | 22 |
| 38 |
Total tardiness = 38
Average tardiness per job = Total tardiness / No. of jobs = 38/6 = 6.33 days
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