 Hello. I am Ishtar Satish Thalange, Assistant Professor, Department of Civil Engineering, Volchian Institute of Technology, SELOP. In today's session, we are going to see the critical path method for project management. At the end of the session, the students are going to compare the critical path method network with the GAN chart for the project management. Now, let's see what is the critical path method. In short, it is also called as CPM. Critical path method is a graphical and logical presentation of the project and its activities. It was developed by the Volker and Hakili. It is used for the repeated type of projects and it is an activity-oriented network technique. It is a deterministic approach type of technique because as it is used for the repeated type of projects, here the particularly deterministic times are being derived. Here, this is a particularly AOA type of network technique. In this particular, CPM is represented by activity on aero type. The critical activities and the critical activity path are being derived with the particularly activity times. Here, the critical path is the longest path in the particular network diagram which is going to help us to derive the project duration or you can say overall project duration of the network. If there are more than one critical path, then the longest path is used to define the critical path and it is used to define the project duration. Now, let's start with the event time. In this particular diagram, we are observing the yellow clear box which are representing the event times. The above and the below are both the event times of first. Here, it is the earliest event time which is represented with the capital T at the foot E. When we observe this yellow bracket, we see that capital E E 1 means what? It is the earliest event time of event 1. And similarly for the event 2, 3 and 4, we are representing capital T E 2, capital T E 3 and capital T E 4. And here in the below yellow color box, here we are representing the capital T L 1 which is the latest event time. It is a backward moving time calculation. And the earliest event time is a forward moving time calculation. Forward moving means what? From left hand side to right hand side. Here, we will move from particular right hand here, from this left hand side to the right hand side for the earliest event time and from the right hand side to the left hand side for the latest event time calculations. Here, the particular T L 1 is the latest time of event 1 and T L 2 is the latest time of particular event 2. These are the deliberations that is small t 1 2. This 1 2 or nothing else is representing this is a time between event 1 2 and T 2 3 is nothing else. It is a division of activity B between event 2 and 3. So, to calculate the particular event, earlier event and the latest event times as we have said forward movement and backward movement. Here, we have to say that T E 1 is equal to 0 because it is starting and here T E 2 is 3 because 0 plus 3 is equal to 3. Similarly, we have to see for the forward events that is 3 plus 2 that is 5, 5 plus 3 is 8. And we have to carry same time of the particular earliest event time to the latest event time 8. 8 minus 3 is equal to 5. Now, let us see the activity time. The activity times are 4 times. Earlier start time, earlier finish time, latest start time and latest finish time. Here, earlier start time is a time of the activity which should start as early as possible. And earliest finish time is a time of the activity means it should activity should finish as earliest it should finish. Here, particularly activity A, B and C. Here, its earliest time is 0 because as it is a starting activity and its still event is 1, its earliest event time is 0 that 0 is equal to we have to that is why the earliest starting time is 0. This 0 plus 3 is equal to 3 that is the earliest finishing time. And similarly, this particular time is the earliest event time of event 2. So, I will write here 3. 3 will is as it is a tail event of activity B, it will be earlier starting time of activity B. Now, 3 is a we have to mention here 3 plus 2 5. Similarly, we have to carry for the activity C. Now, the backward path we have to see as we have obtained the earliest starting time and the earliest finishing time for all the activities from moving from the left hand side to the right hand side. We have to derive the latest start time and latest finish time of the each activity moving from right hand side to the left hand side. Here, once we get the latest event time of activity of event 4 that is 8. We have to mention here the latest finish time time is equal to particularly latest event time that is 8, 8 minus 3 it is 5. Here the latest starting time of activity C is 5. Now, this is equal to particularly the latest event time of particular 3. This 5 which is again equal to latest finishing time of activity B. This 5 minus 2 it is again 3. Similarly, we have to move from right hand side to the left hand side. We will get the particularly latest start time as a finish time. This is a overall time calculations of particularly event as well as the activity. Now, this is a forward path. This is a forward path and backward path. How to define the forward path? As I earlier told that forward path is nothing else it is moving from left hand side to the right hand side of the network. Here in this particular diagram the particularly forward paths are represented by the black color arrows above this particular red arrows. This particular arrows are moving from left hand side to the right hand side. And backward path is a path which is obtained or which is used to derive the latest time moving from the right hand side to the left hand side. In this particular network diagram the backward path is represented by the red color arrows. We are going to construct the network diagram as we move from the forward path direction. The maximum times are taken for the next forward activity. Here and during the backward path the minimum times are taken for the latest times. Later we will see in the particular example. Here the float of the activity. The float of activity is nothing else. It is a flexible range of time of a particular activity in the project by which that particular activity can be delayed without affecting the overall project duration. Here the float is obtained by the difference between the latest start time and latest or you can say earlier start time or you can say latest finish time and earliest finish time of the particular activity. Here there is a calculation of the particular floats of the each activities. The particular float LST minus EST when we take the example of A the LST is 0 and the EST is 0. 0 minus 0 we are getting 0 means what this particularly activity is having the 0 float which is mean as critical activity. When we see that activity B here the LST minus EST here the particular B activity LST is 5 and particularly EST is 3 5 minus 3 we are getting 2. Here the particular float is more than 0 so it is this particular activity B is non-critical activity means what? In short the float if it is equal to 0 that particular activity is critical one if float is more than 0 that particular activity is non-critical activity. Here the critical activities are represented by the arrows and the particular critical path is defined by the event as well as activity. Today's question this is a question here we are going to construct the network diagram and the Gantt chart for the following project. This is the network diagram of our question. In this network diagram when we have calculated all the event times and the activity times we are getting the activities as two critical activities and two non-critical activities. Here when we go for the construction of the Gantt chart of the particular problem this is a Gantt chart construction of a particular problem. When we start to compare between this particular network diagram and the Gantt chart here in the Gantt chart we won't see any critical path or you can say critical activity representation but in the network diagram when we go for the construction we when we see the floats of particular activities we come to know activity B and D are the critical one which needs a more or you can say a more overview and continuous monitoring for that particular activity to start and the complete and the activity A and B A and C are the non-critical activity but this particular representation is not been there in the Gantt chart and here in the network diagram we see the interdependency of the particular activities can be shown easily but in the bar chart it is the major drawback as is that here the interdependency is representation is not there. This is the drawback of between you can say drawback of the Gantt chart when compared with the network diagram. This is a reference for today's session. Thank you.