ITPEC FE Subject A April 2024 Question 41
The activities and milestones of a project are shown in the arrow diagram below. Which of the following is an appropriate description of the project if the duration of activity B is increased by 5 days?
Explanation
The minimum completion time does not change — activity B has 10 days of float, so a 5-day delay is absorbed.
Earliest milestone times with B = 5 days (the dummy lets the end of C feed the milestone after B):
- •Milestone after B: max(10 + 5, 10 + 0) = 15
- •Milestone after D: max(10 + 25, 15 + 10) = 35
- •Milestone before H: max(15 + 20, 35 + 15) = 50
- •Finish: 50 + 15 = 65 days, critical path C → D → G → H
With B = 10 days the milestone after B moves to 20, but the milestone after D stays at max(35, 20 + 10) = 35 and the one before H at max(20 + 20, 50) = 50. The finish stays at 65 days: the longest path through B, A → B → E → G → H, grows from 55 to 60 days and is still shorter than 65.
Answer (c)
Why not others:
- •(a) — G starts when both D and E are done; its earliest start stays at day 35 because the D branch (day 35) still arrives after the E branch (day 30)
- •(b) — a latest start is computed backwards from the finish: F must end by day 50, so it must start by day 30 whatever the duration of B
- •(d) — would hold only if B were on the critical path; B has 10 days of float and the delay uses only 5
Key rule: Lengthening an activity delays the project only by the amount the delay exceeds that activity's total float.
Project Management · AI-written, may contain errors
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