Question

TWA is scheduling the repair of five identical 707 aircraft next month. The time to repair each of the aircraft is given below: Aircraft: 1 2 3 4 5 Repair Time (Days): 6 7 2 5 8 If the sequence of repair were 1-2-3-4-5, what would the mean job flow time be for the aircraft?

a. 14 b. 16.4 c. 28 d. 82

Answer 1

To calculate the mean job flow time we have to first calculate the flow time for each job which is the cumulative sum of the processing time .

If the sequence of repair is 1-2-3-4-5, the flow time for each job are calculated as follows

Job processing time flow time

1 6 6

2 7 13 (As 6+7)

3 2 15 (As 13+2)

4 5 20 (As 15+5)

5 8 28 (As 20+8)

Mean flow time = Sum of the flow time for each job/Number of jobs

= (6+13+15+20+28) / 5

= 82/5

= 16.4

So the answer is option b