In a Critical Path Method (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. Activities A and B can start simultaneously, and Activity C cannot start until both A and B are complete. What is the total project duration?
Correct Answer
D) 11 days
Since A (5 days) and B (8 days) run concurrently, the longest path is B at 8 days. Activity C (3 days) starts after both are complete, so total duration is 8 + 3 = 11 days.
Why This Is the Correct Answer
In CPM scheduling, when activities run concurrently, the critical path is determined by the longest duration activity. Activities A (5 days) and B (8 days) start simultaneously, so B becomes the controlling factor at 8 days. Activity C (3 days) cannot begin until both A and B finish, creating a sequential relationship. Therefore, the total project duration is 8 days (longest concurrent path) + 3 days (sequential activity C) = 11 days.
Why the Other Options Are Wrong
Option A: 13 days
This incorrectly adds all three activity durations (5 + 8 + 3 = 16 days) as if they were sequential. However, Activities A and B run concurrently, not one after the other, so their durations should not be added together.
Option B: 8 days
This only accounts for Activity B's duration (8 days) and ignores Activity C entirely. While B is the longest concurrent activity, C must still be completed after both A and B finish, adding 3 more days to the total.
Option C: 16 days
This adds Activities A and B sequentially (5 + 8 = 13 days) then adds C (13 + 3 = 16 days). This is incorrect because A and B run simultaneously, not consecutively, so only the longer duration (8 days) should be used.
Memory Technique
Remember 'Concurrent = MAX, Sequential = ADD' - when activities run at the same time, take the maximum duration; when they follow each other, add the durations.
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