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GATE CSE 2021 Set 1 Q35: Minimum average waiting time for bursts of 16, 20 and 10 ms

Question

Three processes arrive at time zero with CPU bursts of 16, 20 and 10 milliseconds. If the scheduler has prior knowledge about the length of the CPU bursts, the minimum achievable average waiting time for these three processes in a non-preemptive scheduler (rounded to nearest integer) is ________ milliseconds.

Try it: numerical answer: type the value

Numerical answer. No negative marking.
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Answer: 12 (official GATE 2021 final answer key)

Concept used: Shortest Job First minimises the average waiting time when all jobs arrive together.

First step: Run the bursts in the order 10, 16, 20 and average their start times.

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Source: official GATE 2021 Set 1 CS question paper and final answer key, organised by IIT Bombay. Question paper · Answer key

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