GATE 2024 PI – Question 41
Activities A,B,C have no predecessors; D follows A,B; E follows B,C; F follows A,B. Find the minimum dummy activities for an activity-on-arrow network.
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Correct answer: (D) 3
Explanation
A and B must merge before D,F, while B and C must merge before E. Let A end at event U, B at V and C at W. Add dummy V→U and dummy V→W to enforce the two distinct predecessor combinations. From U, draw D to the finish and F to a separate event, then a third dummy from that event to the finish; this avoids duplicate arrows with identical endpoints for D and F. E runs W→finish. Thus **three dummies, D**, are sufficient and needed under the standard unique-arrow AOA convention.