The critical path is the longest path of duration from the project start to its completion. In this example, the critical path is the sum of duration for tasks ACFHKL AT 26 days. You can find this answer by finding the duration of each path in the project network diagram; the longest path, the critical path, also represents the project’s duration. While it is true that all activities must be completed for the project to be complete, the question asked for the project’s duration.