CISA Practice Question: Information Systems Operations and Business Resilience
A company's availability monitoring shows that a critical application has an average MTBF of 720 hours and an average MTTR of 4 hours. What is the availability percentage?
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 ≈ 0.994475, 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.
- ✗
99.72%
Why it's wrong here
Incorrect calculation.
- ✗
99.17%
Why it's wrong here
Incorrect calculation.
- ✗
99.95%
Why it's wrong here
This would require MTBF much higher or MTTR lower.
- ✓
99.45%
Why this is correct
Calculated as 720/(720+4)=0.9945.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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