Practice Question: Length of an Activity Based on Critical Path

NCEES Civil PE Specification Project Planning: Project schedules

Problem

The activity-on-node network pictured represents a construction schedule. If the schedule's critical path is dependent on Activities AEG (shown in RED), determine the maximum length of Activity D to the nearest day.

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Solution

Answer: C) 9 days

A project’s critical path is the minimum length it takes to complete the schedule.
If the critical path is based on the total length of activities AEG, then the total maximum length of activities ADF will be one less than the length of AEG.

Total Length of AEG:
$$ AEG\ =\ 15\ days\ +\ 7\ days\ +\ 12\ days\ =\ 34\ days $$
Maximum Length of ADF (to keep AEG as the critical path):
$$ ADF\ =\ AEG-1=33\ days $$
Solving for Maximum Length of Activity D:
$$ 33\ days=A+D+F $$
$$ 33\ days=15\ days+D+9\ days $$
$$ D=9\ days $$