Using Critical Path Method (CPM) to Find the Critical Path
A project manager is developing the project schedule and wants to determine the critical path. The activity network diagram shows multiple paths. Which technique should the project manager use?
Quick Answer
The answer is the Critical Path Method (CPM). This technique is correct because it systematically calculates the longest path through the activity network diagram by determining early start, early finish, late start, and late finish dates for every activity, identifying those with zero total float that form the critical path and dictate the shortest possible project duration. On the PMP exam, this question tests your ability to distinguish CPM from other scheduling tools like PERT or schedule compression techniques; a common trap is confusing the critical path with the path having the most activities rather than the longest duration. To remember, think of CPM as the “zero-float finder” — if an activity has no slack, it’s on the critical path.
⚠ Common exam trap
Watch out — candidates often confuse PERT with CPM because both involve network diagrams, but PERT is for estimating durations under uncertainty while CPM is specifically for identifying the critical path using deterministic durations.
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
✓
Critical Path Method (CPM)
The Critical Path Method (CPM) is the correct technique because it is specifically designed to identify the longest path through a project's activity network diagram, which determines the shortest possible project duration. By calculating early start, early finish, late start, and late finish dates for each activity, CPM reveals which activities have zero float and thus constitute the critical path. This directly answers the project manager's goal of determining the critical path from the network diagram.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Resource leveling
Why it's wrong here
Resource levelling adjusts start and finish dates to resolve over-allocation; it alters the schedule rather than computing which path has zero float. It is tempting because levelling can change the critical path, and would be correct after the path is known and resource conflicts must be resolved.
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Gantt chart
Why it's wrong here
A Gantt chart displays schedule bars against a timeline; it does not calculate float or identify the longest path through a network. It is tempting because Gantt charts are the standard schedule presentation format, and would be correct when communicating an already-derived critical path to stakeholders.
- ✓
Critical Path Method (CPM)
Why this is correct
CPM calculates early and late start/finish dates through forward and backward passes, then identifies the longest-duration path as the critical path. This directly satisfies the stem's requirement to determine the critical path from the activity network diagram.
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Program Evaluation and Review Technique (PERT)
Why it's wrong here
PERT uses three-point weighted estimates to handle duration uncertainty; it does not itself determine the critical path. It is tempting because PERT is often paired with critical path method, and would be correct when activity durations are uncertain and expected times must be calculated before path analysis.
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Same concept, more angles
1 more way this is tested on PMP
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Refer to the exhibit. What is the critical path duration?
easy- A.9 days
- ✓ B.11 days
- C.10 days
- D.12 days
Why B: The critical path is the longest path through the network diagram, determining the shortest possible project duration. By summing the durations along each path, Path A-C-D totals 11 days, which is longer than the other paths, making 11 days the correct critical path duration.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PMP practice question is part of Courseiva's free PMI 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 PMP exam.