CISA Practice Question: Information Systems Operations and Business Resilience
An organization's availability management team reports that a critical server has an MTBF of 720 hours and an MTTR of 4 hours. What is the availability percentage for this server?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
99.45%
Availability = MTBF / (MTBF + MTTR) = 720 / (720 + 4) = 720/724 ≈ 0.9945, or 99.45%.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
99.45%
Why this is correct
Correct: 720/(720+4) = 720/724 ≈ 99.45%.
- ✗
99.56%
Why it's wrong here
Incorrect: This might result from miscalculation, e.g., 724/728.
- ✗
99.72%
Why it's wrong here
Incorrect: This would be the result if MTBF were higher.
- ✗
99.89%
Why it's wrong here
Incorrect: This is too high for the given values.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CISA practice question is part of Courseiva's free ISACA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISA exam.