ITPEC FE Morning April 2019 Question 51

Which of the following is an appropriate explanation of the PERT diagram as shown in the figure below?

A2B4C2F4D2G4H5
LegendActivity nameNumber of daysrequired

Explanation

Removing F ends the project 1 day earlier — F lies on the 12-day critical path, and without it the longest path is 11 days.

The diagram has three paths from start to finish:

  • •A – C – G: 2 + 2 + 4 = 8 days
  • •B – F – G: 4 + 4 + 4 = 12 days (critical path)
  • •B – D – H: 4 + 2 + 5 = 11 days

The project takes 12 days. If F is no longer needed, path B – F – G disappears and the longest remaining path is B – D – H at 11 days, so the project finishes 1 day earlier.

Answer (c)

Why not others:

  • •(a) — A – C – G is the shortest path at 8 days; the critical path is the longest one, B – F – G
  • •(b) — 11 days is the length of B – D – H, not of the critical path; the project needs 12 days
  • •(d) — H has 1 day of float (12 − 11); a 2-day delay makes B – D – H 13 days, so the project slips by only 1 day

Key rule: A change on a non-critical path affects the end date only by the amount it exceeds that path's float; shortening the critical path helps only until another path becomes critical.

Project Management · AI-written, may contain errors

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