the Ready pile.
Referring to Figure 3.2, you see that tasks A, F, and H have the Start task as predecessors. In fact, the Start task is the only predecessor for those tasks, so when you cross out the Start task, you move tasks A, F, and H into the Ready pile. Figure 3.3 shows the new arrangement.
Figure 3.3 After one round, the Start task is positioned and tasks A, F, and H are in the Ready pile.
4. Return to step 2 and repeat until you have positioned the Finish task.
To do that, position tasks A, F, and H because they’re in the Ready pile. Then cross them out for any tasks that are still in the Pending pile. When you cross out those tasks, task B loses its last predecessor so move it into the Ready pile. Figure 3.4 shows the new arrangement.
Figure 3.4 After two rounds, the Start task and tasks A, F, and H are positioned. Task B is in the Ready pile.
5. Return to step 2 and repeat until you have positioned the Finish task.
This time position task B and remove it from the remaining tasks’ predecessor lists. After you cross task B off, tasks C and I have no more predecessors so move them to the Ready pile. Figure 3.5 shows the new arrangement.
Figure 3.5 After three rounds, the Start task and tasks A, F, H, and B are positioned. Tasks C and I are in the Ready pile.
By now you probably have the hang of it. Position tasks C and I, and remove them from the Pending tasks’ predecessor lists. That removes the last predecessors from tasks D, E, and G, so move them to the ready pile, as shown in Figure 3.6.
Figure 3.6 After four rounds, only the Finish task is still in the Pending pile.
In the next round, position tasks D, E, and G, and move the Finish task to the Ready pile. Then one final round positions the Finish task.
Now draw arrows showing the predecessor relationships between the tasks. You may need to adjust the spacing and vertical alignment of the tasks to make the arrows look nice. Figure 3.7 shows the final result.
Figure 3.7 This PERT chart shows the paths of execution of the project’s tasks.
To check your work, you can verify that each task has one arrow entering it for each of its predecessors. For example, task G has two predecessors, so it should have two arrows entering it.
Critical Path Methods
PERT charts are often used with the critical path method, which was also invented in the 1950s. That method lets you find critical paths through the network formed by a PERT chart.
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