CISA Practice Question: Information Systems Operations and Business Resilience
A system has a Mean Time Between Failures (MTBF) of 200 hours and a Mean Time To Repair (MTTR) of 20 hours. What is the availability of the system?
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
✓
90.9%
Availability = MTBF / (MTBF + MTTR) = 200 / (200 + 20) = 200 / 220 ≈ 0.909 = 90.9%.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
95.0%
Why it's wrong here
This would require a much higher MTBF or lower MTTR.
- ✗
91.0%
Why it's wrong here
Close but not exact.
- ✗
90.0%
Why it's wrong here
This is slightly lower than the calculated value.
- ✓
90.9%
Why this is correct
Correct calculation: 200/(200+20)=0.909.
Go deeper
Related to this question
About these practice questions
One of 995 original CISA practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
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.