Chapter6
Question2. Consider table 6.3network diagram data for a small project. All duration estimates or estimated times are in days; and the network proceeds from node 1 to node 9.
) Draw an AOA network diagram representing the project .Put the node numbers in the circles and draw arrows from node to node, labeling each arrow with the activity letter and estimated time.
b)Identify all the paths in the network diagram and note how long they are, using figure 6-8 as a guide for how to represent each path.
c) What is the critical path for this project and how long is it?
d) What is the shortest possible time that it will take to complete this project?
e) Review the online tutorials for Gantt and PERT charts in the third suggested Reading by Mark Kelly in this chapter . Write one page paper with your answers to the questions in the tutorials. Also include any questions you had in the tutorials.
b) Path 1: A-B-E-H-K length=2+2+2+2+2=10 Days
Path 2: A-C-F-H-K length=2+3+3+2+2=12 Days
Path 3: A-C-F-I-J-K length=2+3+3+5+1+2=16 Days
Path 4: A-D-G-J-K length=2+4+6+1+2=15 Days
c) The critical path of the project is A-C-F-I-J-K because it is the longest path through the network.
d) The shortest possible time needed to complete this project is 16 Days
e)
Gantt chart tutorials
1) What is the first milestone in this project?
Ans: the first milestone in the project is “sign contract”. That is in the first day of the project that is on 30th November 2000.
2) How much 'slack' time is there after commencement of the alterations, including weekends?
Ans: the commencement date of alteration is 11th December 2000, and the activity is “Prepare site”. As the definition explains that the slack time is the expanded time scale, Therefore if task 11 is extended to 5 days more, the working days is still 3 days expanded because there is Saturday and Sunday also in those extended days. The length of the critical path for the project (8, 9, 11, 12) is 7days (1+2+3+1) excluding weekends. The alternate path for the project can be 8, 9, 10, and 12 since task 10 & 11 overlaps. Thus the alternate path takes 6 days (1+2+2+1). The only difference is of 1 day. But this demonstrates that if task 10 is really very difficult and time consuming then the slack time of 3 days can be added including weekends. They can also work in the weekends to complete the project in time.
3) The supplier of the cable has just informed you that the cable delivered to you is faulty and the replacement cable will not arrive until the end of Monday 18 December. What impact will this have on the end date?
Ans : If such things happen in the project then it will surely have an effect on the finishing date of the project. The ending date will be definitely shift a bit. Here as the delivery of cable will be in 18th December, then only the cabling can be started. Thus cabling will be started on 19th of December shifting the end date of the project to 22nd December.
\4)What options would a project manager have if the cable was arriving on 21 December and the due date still had to be met?
Ans: If such situation is faced then the things that can be done are:
Work day and night for 24 hours,
Bring more workers,
Reduce the task
Improve work efficiency.
PERT Practice
1) Which tasks are on the critical path of the PERT chart above?
Ans: the critical path for the PERT chart is A, B, D, F, I because it is the longest path in chart which takes about 14 days.
2) What is the slack time for tasks C, D and G?
The slack time for task C is one day. Since C & E takes 5 days to complete the task from starting node to the ending node whereas D& F takes 6 days to complete the task from starting node to ending node. Therefore, either task C or task E could take one extra day to finish without disturbing the task that after the starting node of C.
For D there is no slack time because it is in the critical path.
For G, path B, C, E=3+1+4=8
Path 2: B-D-F=3+3+3=9
Path 3: G+H=2+5=7
Therefore the slack time for G is 9-7=2 days.
3) The person working on task C tells the project manager he can't start work until one day after the scheduled starting date. What impact would this have on the completion date of the project?
Ans: if the task E is delayed be 1 day it could have a great impact on the project because other task are also dependent on this task. But regarding the situation of this project, there is a 1 day slack time for task C, thus C can use its slack time and it will have no impact on the project.
4: Task A will be delayed by 2 days because some equipment has arrived late. If the project manager still wants to finish the project within the original time frame, he will need to shorten the time for one or more of the tasks. What steps can he take to reduce the number of days allocated to a task?
It is a common sense question. How can we finish the task faster? It’s obvious that we can either assign more people, or work more hours, or increase the efficiency of the work.
5: The project manager decides to reduce the time needed for tasks D and F by one day each. How effective will this reduction be in achieving his aim of maintaining the original finish time for the project?
D & F falls in the critical path. Thus reducing the time in D & F by one day each makes the initial critical path shorter by 2 days that means it is no longer the critical path. The completion date for this task is reduced to 12 days. The new critical path is A, B, C, and E, I which takes 13 days to complete. Thus Reducing tasks D and F each by one day would only shorten the project by one day since after a 2 day reduction.