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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.

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  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 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 at 14:01

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