Question

What is the use of ‘dummy' in CPM network. 
• [A.] To give a start, that is a starting activity 
• [B.] To give logical representation in a network having an activity common in two operations running parallel to each other 
• [C.] To prevent two arrows having common beginning and end points 
• [D.] To represent the longest time taking activity in the network 
• [E.] To represent the shortest path of the network Choose the correct answer from the options given below :

• A. A and B
• B. B and C
• C. C and D
• D. D and E

Hint:

Dummy activities in CPM/PERT:
• Shown using dotted arrows
• Have zero duration
• Maintain logical dependency in networks They are used only for correct network representation.

Answer 1

The Correct Option is B

Concept: In CPM (Critical Path Method) and PERT networks, a dummy activity is an activity that:
• Consumes no time
• Requires no resources
• Is represented by a dotted arrow Dummy activities are introduced only to maintain proper logical relationships in the network diagram.

Step 1: Analyze statement A.
A dummy activity is not used to represent the starting activity of a project. Hence, statement A is incorrect.

Step 2: Analyze statement B.
Dummy activities are used to maintain logical relationships between parallel activities and dependent operations. Hence, statement B is correct.

Step 3: Analyze statement C.
In CPM networks, dummy activities help avoid two arrows having the same start and end nodes. Hence, statement C is correct.

Step 4: Analyze statement D.
The longest duration path is represented by the critical path, not by a dummy activity. Hence, statement D is incorrect.

Step 5: Analyze statement E.
Dummy activities are not used to represent the shortest path of the network. Hence, statement E is incorrect.

Step 6: Choose the correct option.
Correct statements are B and C. Therefore, the correct answer is: \[ {\text{(B) B and C}} \]