Network Diagram

 In one of the questions about critical chain method, the question stated something like:

Task 1 is preceded by task 2 and has a estimated duration of 1 week

Task 1 is preceded by task 3 and has a estimated duration of 4 weeks

- so in the above scenario how can Task 1 take 1 week in one case and the same task take 5 weeks in another case ? 

 

Please write full question(ditto), otherwise what is written here is vague and cant be answerable.