CST Critical Path & Float Analysis 2 — Questions and Answers
Question 1: A project activity has an Early Start of day 10, Late Start of day 15, Early Finish of day 20, and Late Finish of day 25. What is the Total Float?
- 5 days (Correct answer)
- 10 days
- 0 days
- 15 days
Correct answer: 5 days
Total Float = Late Start − Early Start (or Late Finish − Early Finish) = 15 − 10 = 5 days.
Question 2: Which of the following best describes Free Float?
- The amount of time an activity can be delayed without delaying the project end date
- The amount of time an activity can be delayed without delaying the Early Start of any successor (Correct answer)
- The total slack available across all project activities
- The difference between an activity's Late Finish and Early Finish
Correct answer: The amount of time an activity can be delayed without delaying the Early Start of any successor
Free Float is the amount of time an activity can be delayed without affecting the Early Start of any immediate successor.
Question 3: On a network diagram, Activity A (duration 4) → Activity B (duration 3) → Activity C (duration 5). Activity A also connects to Activity D (duration 6) → Activity C. Which path is critical?
- A → B → C with duration 12
- A → D → C with duration 15 (Correct answer)
- Both paths are critical
- Neither path is critical without knowing float
Correct answer: A → D → C with duration 15
Path A→D→C = 4+6+5 = 15 days; Path A→B→C = 4+3+5 = 12 days; the longest path (15 days) is the critical path.
Question 4: An activity on the critical path has its duration increased by 3 days. What is the effect on the project?
- Project duration increases by 3 days (Correct answer)
- Project float increases by 3 days
- No effect if the activity has free float
- The critical path shifts to another path
Correct answer: Project duration increases by 3 days
Any duration increase on a critical path activity directly extends the project end date by the same amount.
Question 5: What does Interfering Float (also called Interfering Slack) represent?
- Float that belongs exclusively to a single activity
- The difference between Total Float and Free Float (Correct answer)
- Float shared among all activities on the critical path
- Negative float indicating a schedule overrun
Correct answer: The difference between Total Float and Free Float
Interfering Float = Total Float − Free Float, representing float that, if used, would delay a successor's Early Start.
Question 6: In CPM scheduling, what condition must exist for two activities to be considered 'parallel'?
- They must have the same duration
- They do not have a dependency relationship and can be executed simultaneously (Correct answer)
- They must both be on the critical path
- They share the same resources
Correct answer: They do not have a dependency relationship and can be executed simultaneously
Parallel activities have no dependency relationship between them and can therefore be performed concurrently.
Question 7: A project scheduler identifies that Activity X has a Total Float of −4 days. What does this indicate?
- Activity X has 4 days of schedule buffer
- Activity X is on the critical path with zero float
- Activity X is behind schedule and the project will be late unless corrective action is taken (Correct answer)
- Activity X can be delayed 4 days without impacting the project
Correct answer: Activity X is behind schedule and the project will be late unless corrective action is taken
Negative Total Float means the activity cannot meet its constraint or deadline even if started at the earliest possible time, indicating a schedule overrun.
CST Critical Path & Float Analysis 2
A project activity has an Early Start of day 10, Late Start of day 15, Early Finish of day 20, and Late Finish of day 25.
What is the Total Float?