Operations research
Spot it
Spot the critical path mistake
Can you spot the mistake in this lecture hall schedule?
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Lesson notes
Draw a project network, find critical path, floats and PERT expected times
Key points
- Path A-B-D lasts 4 plus 6 plus 5, which is 15 weeks.
- Path A-C-D lasts 12 weeks, which is shorter, so it is not the critical path.
- Activity C starts earliest at week 4 and latest at week 7.
- Total float of C is latest start minus earliest start, so 3 weeks.
Takeaway: Critical path is the longest path; its activities have zero float.
Quick check: Which step is wrong?
- Step 1
- Step 2
- Step 3
The critical path is the longest path, not the shortest one.
critical pathtotal floatexpected time
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