GATE 2017 ME (ME1) – Question 62

Production Planning and Control · Aggregate production planning, scheduling and material requirement planning · 2 marks · Numerical answer

Four jobs P, Q, R, S are available together for one machine. Their processing times are 15, 9, 22 and 12 days respectively. Find the shortest possible average flow time in days.

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Correct answer: 31 to 31

Explanation

When all jobs are available at time zero, shortest-processing-time order minimizes the sum of completion times. The order is Q, S, P, R, with completion times $9,9+12=21,21+15=36,36+22=58$ days. Average flow time is $(9+21+36+58)/4=124/4=31$ days.

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