Chapter 9 Answer Key
9.1: Reducing Project Duration
Questions: Reducing Project Duration
1. $200 per day
2. Have the most slack; Are the least expensive to crash
3. True
4. False
5. False
Exercise 1.B: Initial Network
Critical Path 1: A->B->D->G
Duration: 33
Critical Path 2: A->C->E->F->G
Duration: 38
Project Duration: 38
Total Direct Costs: $9,700
Exercise 1.C: Crashing
Critical Path 1: A->B->D->G
Duration: 32
Critical Path 2: A->C->E->F->G
Duration: 37
Project Duration: 37
Normal Duration Direct Costs: $9,700
Additional Costs of Crashing: $100 (A)
Total Cost at this time period: $9,800
Critical Path 1: A->B->D->G
Duration: 32
Critical Path 2: A->C->E->F->G
Duration: 36
Project Duration: 36
Normal Duration Direct Costs: $9,700
Additional Costs of Crashing: $100 (A) + $400 (E)
Total Cost at this time period: $10,200
Critical Path 1: A->B->D->G
Duration: 32
Critical Path 2: A->C->E->F->G
Duration: 35
Project Duration: 35
Normal Duration Direct Costs: $9,700
Additional Costs of Crashing: $100 (A) + $400 (E) + $600 (C)
Total Cost at this time period: $10,800
Critical Path 1: A->B->D->G
Duration: 32
Critical Path 2: A->C->E->F->G
Duration: 34
Project Duration: 34
Normal Duration Direct Costs: $9,700
Additional Costs of Crashing: $100 (A) + $400 (E) + $600 (C) + $600 (C)
Total Cost at this time period: $11,400
Critical Path 1: A->B->D->G
Duration: 32
Critical Path 2: A->C->E->F->G
Duration: 33
Project Duration: 33
Normal Duration Direct Costs: $9,700
Additional Costs of Crashing: $100 (A) + $400 (E) + $600 (C) + $600 (C) + $1,500 (F)
Total Cost at this time period: $12,900
Critical Path 1: A->B->D->G
Duration: 32
Critical Path 2: A->C->E->F->G
Duration: 32
Project Duration: 32
Normal Duration Direct Costs: $9,700
Additional Costs of Crashing: $100 (A) + $400 (E) + $600 (C) + $600 (C) + $1,500 (F) + $1,500 (F)
Total Cost at this time period: $14,400
Exercise 1.D: Total Costs
| Initial Dur | -1 | -2 | -3 | -4 | -5 | -6 | -7 | |
| Project Duration | 38 | 37 | 36 | 35 | 34 | 33 | 32 | NA |
| Total Direct Costs | $9,700 | $9,800 | $10,200 | $10,800 | $11,400 | $12,900 | $14,400 | NA |
| Incentives ($500 per day that project is delivered early) | – | $500 | $1,000 | $1,500 | $2,000 | $2,500 | $3,000 | NA |
| TOTAL COSTS | $9,700 | $9,300 | $9,200 | $9,300 | $9,400 | $10,400 | $11,400 | NA |
The optimum time period in terms of total cost is crashing the project by 2 days
Exercise 2.B: Initial Network
Critical Path: B->C->F->G
Project Duration: 40
Total Direct Costs: $14,200
Exercise 2.C: Crashing
Critical Path: B->C->F->G
Project Duration: 39
Normal Duration Direct Costs: $14,200
Additional Costs of Crashing: $100 (B)
Total Cost at this time period: $14,300
Critical Path: B->C->F->G
Project Duration: 38
Normal Duration Direct Costs: $14,200
Additional Costs of Crashing: $100 (B) + $300 (G)
Total Cost at this time period: $14,600
Critical Path: B->C->F->G
Project Duration: 37
Normal Duration Direct Costs: $14,200
Additional Costs of Crashing: $100 (B) + $300 (G) + $600 (C)
Total Cost at this time period: $15,200
Critical Path: B->C->F->G
Project Duration: 36
Normal Duration Direct Costs: $14,200
Additional Costs of Crashing: $100 (B) + $300 (G) + $600 (C) + $600 (C)
Total Cost at this time period: $15,800
Critical Paths: B->C->F->G and B->C->E->G
Project Duration: 35
Normal Duration Direct Costs: $14,200
Additional Costs of Crashing: $100 (B) + $300 (G) + $600 (C) + $600 (C) + $1,500 (F)
Total Cost at this time period: $17,300
Critical Paths: B->C->F->G and B->C->E->G
Project Duration: 34
Normal Duration Direct Costs: $14,200
Additional Costs of Crashing: $100 (B) + $300 (G) + $600 (C) + $600 (C) + $1,500 (F) + 1,500 (F) + $500 (E)
Total Cost at this time period: $19,300
Project cannot be crashed to any shorter duration.
Exercise 2.D: Total Costs
| Initial Dur | -1 | -2 | -3 | -4 | -5 | -6 | -7 | |
| Project Duration | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 33 |
| Total Direct Costs | $14,200 | $14,300 | $14,600 | $15,200 | $15,800 | $17,300 | $19,300 | NA |
| Indirect Costs | $3,000 | $2,500 | $2,000 | $1,500 | $1,000 | $500 | $250 | $0 |
| TOTAL COSTS | $17,200 | $16,800 | $16,600 | $16,700 | $16,800 | $17,800 | $19,550 | NA |
The optimum time period in terms of total cost is crashing the project by 2 days
