This LFCS practice question tests your understanding of essential commands. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Refer to the exhibit.
$ top -bn1 | head -5
top - 14:23:45 up 10 days, 2:15, 1 user, load average: 1.5, 2.0, 2.5
Tasks: 123 total, 1 running, 122 sleeping, 0 stopped, 0 zombie
%Cpu(s): 25.0 us, 10.0 sy, 0.0 ni, 65.0 id, 0.0 wa, 0.0 hi, 0.0 si
MiB Mem : 1984.4 total, 500.0 free, 1000.0 used, 484.4 buff/cache
MiB Swap: 2048.0 total, 2048.0 free, 0.0 used. 1484.4 avail Mem
Based on the exhibit, what is the average CPU idle percentage over the last 15 minutes?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
65.0%
The average CPU idle percentage over the last 15 minutes is calculated from the 'idle' value in the 'average' row of the 'mpstat' output. In the exhibit, the 'average' row shows an 'idle' value of 65.0, meaning the CPU was idle 65.0% of the time on average across all CPUs over the 15-minute interval. Therefore, the correct answer is 65.0%.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
65.0%
Why this is correct
The %Cpu(s) line shows 65.0 id (idle).
Related concept
Read the scenario before looking for a memorised answer.
✗
2.0
Why it's wrong here
That is the 5-minute load average.
✗
1.5
Why it's wrong here
That is the 1-minute load average.
✗
2.5
Why it's wrong here
That is the 15-minute load average.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Linux Foundation often tests the ability to correctly identify the 'idle' column in the 'average' row of 'mpstat' output, as candidates may mistakenly pick a value from a per-CPU row or confuse 'idle' with other columns like 'sys' or 'iowait'.
Detailed technical explanation
How to think about this question
The 'mpstat' command reads CPU statistics from /proc/stat, which tracks time spent in various states (user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice). The 'idle' column represents the percentage of time the CPU(s) were idle and not waiting for I/O. In a multi-CPU system, the 'average' row aggregates all CPUs, providing a system-wide view; this is critical for capacity planning and identifying CPU bottlenecks in real-world scenarios.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the LFCS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 65.0% — The average CPU idle percentage over the last 15 minutes is calculated from the 'idle' value in the 'average' row of the 'mpstat' output. In the exhibit, the 'average' row shows an 'idle' value of 65.0, meaning the CPU was idle 65.0% of the time on average across all CPUs over the 15-minute interval. Therefore, the correct answer is 65.0%.
What should I do if I get this LFCS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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