ITPEC FE Morning April 2018 Question 12

Source exam: ITPEC FE Morning April 2018Topic: Computer Systems & Hardware

ITPEC FE Morning April 2018 — Question 12 of 80

HDD Average Rotational Latency — calculate half-rotation time from RPM.

Given: rotation speed = 2000 RPM

  • •Full rotation time = 60,000 ms / 2000 = 30 ms
  • •Average rotational latency = half of full rotation = 30 / 2 = 15 ms

Answer: (b) 15

Why not others:
- (a) 10 — would imply 1/3 of a rotation, not 1/2
- (c) 25 — does not correspond to any meaningful fraction
- (d) 30 — this is the full rotation time, not the average latency

Key rule: Average rotational latency = 60,000 / RPM / 2 (always half a full rotation).

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