I have to calculate the critical path for a project, where activity A and C can start in parallel. Please see the image below

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Since I had two activities that could start in parallel (A and C), I also used the dummy start node. Similarly, since my project had 2 nodes at the end (B and D), I added the dummy end node. Please tell me if my approach is correct.

  1. Yes, adding start and finish milestones to the network is correct. (Calling them "dummy nodes" is unconventional, as that term is usually reserved for activity-on-arrow diagrams.)
  2. You might want to double-check your calculations. Conventional terminology starts the project on Day 1, not Day 0. In addition, your start and finish days are not consistent with the durations shown.
  • Thanks for the reply. Could you please refer to the inconsistency (other than start day being 1)? Isn't the Critical Path Start->C->D->End?
    – Fabiana
    Jan 31 '19 at 3:33
  • Yes, the CP is as you've stated. The problem is in the meaning of the dates. For example, you've shown activity A with an early start on (the morning of) Day 0 and an early finish on (the evening of) Day 2. That's 3 days (0,1,2), which doesn't match the 2-day duration shown. Overall, you've got the project starting on (the morning of) Day 0 and finishing on (the evening of) Day 9 - i.e. 10 days, while it's longest path is clearly 9 days (3+6). The morning/evening distinction is important, and you've left out the required +1/-1 adjustments in your math.
    – Tom Boyle
    Jan 31 '19 at 14:01

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