cpm__pert

- 1 - CA. Parag Gupta Ph.: +91 9891 432 632 Paraggupta_ca@yahoo.co.in Costing & O.R. For notes/updates/amendments on all subjects log on: http://groups.yahoo.com/group/costingbyparaggupta PERT/CPM PERT – Program Evaluation & Review Technique – It is generally used for those projects where time required to complete various activities are not known as a priori. It is probabilistic model & is primarily concerned for evaluation of time. It is event oriented. CPM – Critical Path Analysis – It is a commonly used for those projects which are repetitive in nature & where one has prior experience of handling similar projects. It is a deterministic model & places emphasis on time & cost for activities of a project. Steps for drawing CPM/PERT network: 1. Analyze & break up of the entire project into smaller systems i.e. specific activities and/or events. 2. Determine the interdependence & sequence of those activities. 3. Draw a network diagram. 4. Estimate the completion time, cost, etc. for each activity. 5. Identify the critical path (longest path through the network). 6. Update the CPM/PERT diagram as the project progresses. Network Representation: Each activity of the project is represented by arrow pointing in direction of progress of project. The events of the network establish the precedence relationship among different activities. Three rules are available for constructing the network. Rule 1. Each activity is represented by one & only one, arrow. Rule 2. Each activity must be identified by two distinct events & No two or more activities can have the same tail and head events. Following figure shows how a dummy activity can be used to represent two concurrent activities, A & B. By definition, a dummy activity, which normally is depicted by a dashed arrow, consumes no time or resources. Dummy activity is a hypothetical activity which takes no resource or time to complete. It is represented by broken arrowed line & is used for either distinguishing activities having common starting & finishing events or to identify & maintain proper precedence relationship between activities that are not connected by events. • A project can be defined as a set of large number of activities or jobs (with each activity consuming time & resources) that are performed in a certain sequence determined. • A network is a graphical representation of a project, depicting the flow as well as the sequence of well- defined activities & events. • An activity (Also known as task & job) is any portion of a project which consumes time or resources and has definable beginning & ending. • Event (Also known as node & connector) is the beginning & ending points of an activity or a group of activities. - 2 - CA. Parag Gupta Ph.: +91 9891 432 632 Paraggupta_ca@yahoo.co.in Costing & O.R. For notes/updates/amendments on all subjects log on: http://groups.yahoo.com/group/costingbyparaggupta Inserting dummy activity in one four ways in the figure, we maintain the concurrence of A & B, and provide unique end events for the two activities (to satisfy Rule 2). Rule 3. To maintain correct precedence relationship, the following questions must be answered as each activity is added to the network: (a) What activities must be immediately precede the current activity? (b) What activities must follow the current activity? (c) What activities must occur concurrently with the current activity? The answers to these questions may require the use of dummy activities to ensure correct precedences among the activities. For example, consider the following segment of a project: 1. Activity C starts immediately after A and B have been completed. 2. Activity E starts only after B has been completed. Part (a) of the figure above, shows the incorrect representation of the precedence relationship because it requires both A & B to be completed before E can start. In part (b) the use of dummy rectifies situation. Question 1: What do you mean by a dummy activity? Why it is used in networking? (4 Marks) May/08 Question 2: Depict the following dependency relationships by means of network diagrams.(The Alphabets stands for activities) 1. A and B control F; B and C control G. 2. A and B control F; B controls G while C controls G and H. 3. A controls F and G; B controls G while C controls G and H. 4. A controls F and G; B and C control G with H depending upon C. 5. F and G are controlled by A, G and H are controlled by B with H controlled by B and C. 6. A controls F, G and H; B controls G and H with H controlled by C. Question 3: Develop a network based on the following information; Activity Immediate predecessors A - B - C A D B E C,D F D G E - 3 - CA. Parag Gupta Ph.: +91 9891 432 632 Paraggupta_ca@yahoo.co.in Costing & O.R. For notes/updates/amendments on all subjects log on: http://groups.yahoo.com/group/costingbyparaggupta H F Question 4: Construct the project network comprised of activities A to L with the following precedence relationships: (a) A,B and C, the first activities of the project can be executed concurrently (b) A & B precede D (c) B precedes E,F,H (d) F and C precede G (e) E and H precede I & J (f) C,D,F and J precede K (g) K precede L (h) I, G, and L are terminal activities of the project. Question 5: Construct the project network comprised of activities A to P that satisfies the following precedence relationships: (a) A,B and C, the first activities of the project can be executed concurrently (b) D,E and F follow A (c) I and G follow both B and D (d) H follows both C & G (e) K and L follow I (f) J succeeds both E and H (g) M and N succeed F, but cannot start until both E and H are completed. (h) O succeeds both M and I (i) P succeeds J,L and O (j) K,N and P are the terminal activities of the project. Question 6: A publisher has a contract with an author to publish a textbook. The simplified (activities) associated with the production of the textbook are given below. The author is required to submit to the publisher a hard copy and a computer file of the manuscript. Develop the associated network for the project. Question 7: A project consists of a series of tasks labeled A, B, …., H, I with the following relationships (W