PERT/CPM Problems
1. For the following data, draw the network diagram, and then crash the activities to find the time-cost trade-off points that the company should want to consider. Start with the plan that has the longest duration.
|
Activity |
Preceding Activity |
Time(weeks) Normal Crash Program Program |
Cost ($000s) Normal Crash Program Program |
|
A |
- |
2 2 |
5 5 |
|
B |
A |
5 3 |
11 21 |
|
C |
A |
2 1 |
7 16 |
|
D |
B, C |
4 2 |
8 22 |
|
E |
B |
3 2 |
9 18 |
|
F |
D, E |
3 3 |
9 9 |
2. Draw the network diagram for the following problem and indicate a sequence of plans that the company should want to consider in making a time-cost tradeoff. The company is not interested in reducing the project duration below 29 days. Start with the plan that has the longest duration.
|
Activity |
Preceding Activity |
Time(days) Regular Crash Program Program |
Cost ($) Regular Crash Program Program |
|
A |
- |
10 9 |
5,000 5,200 |
|
B |
- |
14 11 |
3,500 3,950 |
|
C |
A |
8 7 |
4,000 4,100 |
|
D |
A |
7 2 |
2,100 3,600 |
|
E |
B |
5 3 |
2,500 3,000 |
|
F |
B |
10 7 |
2,250 3,750 |
|
G |
C |
9 9 |
5,000 5,000 |
|
H |
D, E |
11 9 |
3,850 5,250 |
|
I |
G, H |
5 3 |
2,375 3,575 |
Answers:
1. The plan with the longest duration takes 14 weeks at a cost of $49,000. The one with the shortest duration takes 10 weeks at a cost of $82,000
2. Beginning plan takes 35 days at a cost of $30,575. Completing the project in 29 days increases the project cost to $32,975