The correct DAX measure is Availability = DIVIDE(SUM([RunTime]), SUM([RunTime])+SUM([DownTime])) * 100. This is the right choice because the DIVIDE function safely handles division by zero—a critical safeguard when calculating availability percentage from runtime and downtime data—and the formula sums both columns across all rows before performing the division, then multiplies by 100 to express the result as a percentage. On the PL-900 exam, this question tests your understanding of DAX measures for common business metrics, often appearing in scenarios involving manufacturing or operational efficiency. A common trap is forgetting to use SUM() around the columns or attempting to divide row-by-row without aggregation, which would yield incorrect totals. Remember the memory tip: "Divide, Sum, then Multiply by 100"—always aggregate first, use DIVIDE for safety, and scale to a percentage to match the availability calculation requirement.
PL-900 Demonstrate the capabilities of Power BI Practice Question
This PL-900 practice question tests your understanding of demonstrate the capabilities of power bi. 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.
A company uses Power BI to monitor manufacturing efficiency. The dataset includes a column 'RunTime' (in minutes) and 'DownTime' (in minutes). A user wants to calculate 'Availability' as (RunTime / (RunTime + DownTime)) * 100. Which DAX measure should be used?
Option A is correct because it uses the DIVIDE function to safely handle division by zero, and multiplies by 100 to express the result as a percentage. The formula sums RunTime and DownTime across all rows, then computes Availability = (Total RunTime / (Total RunTime + Total DownTime)) * 100, which matches the user's requirement exactly.
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.
SUMX is used for row-by-row evaluation but may not aggregate correctly without context.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse aggregate-level calculations (using SUM) with row-level calculations (using SUMX or AVERAGE), and they may forget to multiply by 100 when the requirement explicitly asks for a percentage value.
Detailed technical explanation
How to think about this question
The DIVIDE function in DAX is designed for safe division, returning BLANK (or an alternate result) when the denominator is zero, avoiding division-by-zero errors. In Power BI, measures are evaluated in filter context, so SUM([RunTime]) and SUM([DownTime]) automatically respect any slicers or filters applied to the report, making the measure dynamic. Using SUMX with row-context iteration would require explicit context transition (e.g., using CALCULATE) to respect filters correctly, which is not done here.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
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.
Demonstrate the capabilities of Power BI — This question tests Demonstrate the capabilities of Power BI — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Availability = DIVIDE(SUM([RunTime]), SUM([RunTime])+SUM([DownTime])) * 100 — Option A is correct because it uses the DIVIDE function to safely handle division by zero, and multiplies by 100 to express the result as a percentage. The formula sums RunTime and DownTime across all rows, then computes Availability = (Total RunTime / (Total RunTime + Total DownTime)) * 100, which matches the user's requirement exactly.
What should I do if I get this PL-900 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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