ITPEC FE Morning April 2021 Question 16
ITPEC FE Morning April 2021 — Question 16 of 80
System Availability (MTBF & MTTR) — calculate availability percentage from MTBF and MTTR.
Formula: Availability = MTBF / (MTBF + MTTR) × 100%
Key trap: Units must match — convert MTBF from days to hours first.
- •MTBF =
30 days=720 hours - •MTTR =
6 hours - •Availability =
720 / (720 + 6) × 100%=720 / 726 × 100%≈ 99.17%
Answer: (d) 99.17
Why not others:
- (a) 0.83 — forgot to multiply by 100, and even then the fraction would be 0.9917
- (b) 83.33 — used wrong formula (MTTR in numerator instead of MTBF)
- (c) 98.36 — likely used incorrect MTTR value
Key rule: Always convert MTBF and MTTR to the same unit before applying the formula. ITPEC often gives MTBF in days and MTTR in hours.
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