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A critical path is a directed weighted chain that has maximum value. The critical value represents the minimum time for the completion of all the steps.
• We use Critical Paths for Problems that are based on completing a task involving multiple steps
• Some steps have prerequisites or can be done at the same time
• The critical path is ALWAYS the MAXIMUM VALUE in a directed chain
Critical Path
Beginning A
C
B E
F
G
D
End2
2
4
0
4 3 3 0
7 0
Example 1 (Finding the Critical Path):
1. What is the minimal time to complete this project?
2. While carrying out the project, step D took two extra days and step B took one less day. Did these additional changes influence the minimal completion time for the project? Explain.
The minimal time is the Critical path:BeginningABFEnd2 + 4 + 7 = 13
The minimal time changed from 13 to 12. Still the same Critical Path.
Example 2 (Drawing the Graph):
The following table indicates the different tasks, their completion time and the prerequisite tasks for starting a company:
What is the minimal time required to start this company?
Task Description Time (days) Prerequisites
A Prepare business plan 30 NoneB Conduct Market Research 10 AC Look for partners 25 AD Look for location 20 AE Analyze market research 5 BF Evaluate productdistribution system 15 C and DG Arrange financing 35 E and FH Launch company None G
GRAPHING STEPS: Beginning Prerequisites (connecting edges) End
Beginning EndA G
F
E
D
C
B
H30
10
25
20
5
15
35
35
0 0
15
The minimal time is the Critical path:BeginningACFGHEnd30 + 25 + 15 + 35 + 0 + 0 = 105