PROBLEMS

13.132    Draw the PERT network associated with the following activities.

Immediate Predecessor
A    –
B    A
C    A
D    B
E    B
F    C
G    D
H    E, F
ANSWER:
13.133    Given:
Activity    Optimistic    Most Likely    Pessimistic
A    3    4    5
B    6    7    14
C    2    3    10
D    0.5    1    1.5
E    6    9    12
F    4    5    12
G    1    3    11

 

 

Determine:

(a)    the critical path
(b)    the probability that the project will be completed in 22 weeks

ANSWER:
13.134    The following represent activities in a major construction project.  Draw the network to represent this situation.

Activity    Immediate Predecessor
A    –
B    –
C    A
D    B
E    B
F    C, D
G    E
H    F, G

13.135    A small software development project has five major activities.  The times are estimated and provided in the table below.  Find the expected time for completing this project.

Activity    Immediate
Predecessor    a    m    b
A        2    5    8
B        3    6    9
C    A    4    7    10
D    B    2    5    14
E    C    3    3    3
(a)  What is the expected completion time for this project?
(b)  What variance would be used in finding probabilities of finishing by a certain time?

13.136    A project has an expected completion time of 40 weeks and a standard deviation of 5 weeks.  It is assumed that the project completion time is normally distributed.

(a) What is the probability of finishing the project in 50 weeks or less?
(b) What is the probability of finishing the project in 38 weeks or less?
(c) The due date for the project is set so that there is a 90 percent chance that the project will be finished by this date.  What is the due date?

 

13.137    Development of a new deluxe version of a particular software product is being considered.  The activities necessary for the completion of this are listed in the table below.

Activity    Normal Time    Crash Time    Normal Cost    Crash Cost    Immediate
Predecessor
A    4    3    2000    2600    –
B    2    1    2200    2800    –
C    3    3    500    500    –
D    8    4    2300    2600    A
E    6    3    900    1200    B
F    3    2    3000    4200    C
G    4    2    1400    2000    D,E

(a)    What is the project completion date?
(b)    What is the total cost required for completing this project on normal time?
(c)    If you wish to reduce the time required to complete this project by one week, which activity should be crashed, and how much will this increase the total cost?
13.138    Draw the PERT network associated with the following activities.

Immediate Predecessor
A    –
B    A
C    A
D    B
E    B
F    C, E
G    A, D
H    F
I    F
J    G, H, I
13.139    Given:

Activity    Optimistic    Most Likely    Pessimistic
A    3    4    5
B    6    7    14
C    2    3    10
D    6    9    12
E    4    5    12
F    1    3    11
G    1    2    9
H    2    5    8
I    1    4    7

 

 
Determine:

(a)    the critical path
(b)    the probability that the project will be completed in 22 weeks
13.140    The following table represents activities in a major construction project.  Draw the network to represent this situation.

Activity    Immediate Predecessor
A    –
B    –
C    B
D    B
E    A, C
F    D
G    E, F
H    B
I    G, H
13.141    A small software development project has four major activities.  The times are estimated and provided in the table below.  Find the expected time for completing this project.

Activity    Immediate
Predecessor    a    m    b
A        2    5    8
B        3    6    9
C    A    4    7    10
D    B    2    5    14
E    D    3    3    3
F    C    6    8    10
G    E, F    1    1    1
H    C    6    10    14
I    G, H    3    4    5
(a)    What is the expected completion time for this project?
(b)    What variance would be used in finding probabilities of finishing by a certain time?

13.142    A project has an expected completion time of 50 weeks and a standard deviation of 7 weeks.  It is assumed that the project completion time is normally distributed.

(a)    What is the probability of finishing the project in 50 weeks or less?
(b)    What is the probability of finishing the project in 55 weeks or more?
(c)    What is the probability of finishing the project in 44 weeks or less?
(d)    The due date for the project is set so that there is a 90 percent chance that the project will be finished by this date.  What is the due date?

 

13.143    Development of a new deluxe version of a particular software product is being considered.  The activities necessary for the completion of this are listed in the table below.

Activity    Normal Time    Crash Time    Normal Cost    Crash Cost    Immediate
Predecessor

A    4    3    2,000    2,600    –
B    5    3    2,200    2,800    –
C    3    3    500    500    –
D    8    4    2,400    2,600    A
E    6    3    900    1,200    B
F    3    2    3,000    4,200    C
G    4    2    1,700    2,000    D,E

(a)    If you wish to reduce the time required to complete this project by two weeks, which activity(ies) should be crashed, and how much will this increase the total cost?
(b)  What would be the added cost if you wanted to complete the project in the minimum time possible?

 

SHORT ANSWER/ESSAY

13.144    PERT is the acronym for

13.145    CPM is the acronym for

 

13.146    In a PERT analysis, how is the optimistic time defined?

 

13.147    In a PERT analysis, how is the most likely time defined?

 

13.148    In PERT analysis, how is the pessimistic activity time defined?

 

13.149    In PERT/CPM, what is meant by the critical path?