In a CPM schedule, Activity A has a duration of 5 days, Activity B has a duration of 8 days, and Activity C has a duration of 3 days. If A and B can start simultaneously, and C cannot start until both A and B are complete, what is the total project duration?
Correct Answer
B) 11 days
Since A (5 days) and B (8 days) run concurrently, B finishes last at day 8. Activity C (3 days) starts after B completes, so total duration is 8 + 3 = 11 days.
Why This Is the Correct Answer
In CPM scheduling, when activities run concurrently, the longest duration determines when both are complete. Activities A (5 days) and B (8 days) start simultaneously, so B finishes last at day 8. Activity C cannot begin until both A and B are finished, so C starts on day 8 and runs for 3 days. The total project duration is therefore 8 + 3 = 11 days.
Why the Other Options Are Wrong
Option A: 8 days
This incorrectly adds all three activity durations (5+8+3=16) then subtracts 3, or assumes C starts after A finishes (5+8=13). This ignores that A and B run concurrently.
Option C: 13 days
This only accounts for the duration of Activity B (8 days) and completely ignores Activity C, which must still be completed after both A and B finish.
Memory Technique
Remember 'Concurrent = Controlling': when activities run at the same time, the longest one controls when the next phase can start. Think of it as waiting for the slowest person in your group.
Reference Hint
Look up CPM (Critical Path Method) scheduling in construction management chapters, specifically sections on concurrent activities and project duration calculations.
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