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Critical Path

5 minutes 5 Questions

The Critical Path is the sequence of tasks that forms the longest duration allowing the project to be completed in the shortest time. Any delay in these tasks would directly result in a delay of the entire project. Therefore, they have zero 'float.' Decisive in the CPM, the critical path helps identify the tasks that should be closely managed and controlled to ensure the project's successful and timely completion.

Guide to the Critical Path Method

The Critical Path Method (CPM) is an essential tool in project management. It is a way of calculating the 'critical path' in a project, which is the sequence of tasks that must be completed on time for the entire project to be completed on time.
The critical path is important because it identifies the tasks that directly impact the project's completion date. Delay in any task on the critical path directly impacts the project end date. Thus, understanding CPM is key to effective project scheduling and management.
Here's how CPM works:
1. List all tasks needed to complete the project.
2. Estimate how long each task will take.
3. Determine the dependencies between the tasks.
4. Draw the network diagram.
5. Identify all the paths through the network diagram.
6. Calculate the length of each path.
7. The longest path is the critical path.
Exam Tips: Answering Questions on Critical Path
1. Understand the concept of critical path thoroughly. This is key to answering any high-level questions about its importance or how it works.
2. Practice drawing network diagrams. Many exam questions may require you to draw a network diagram and identify the critical path.
3. Be comfortable with calculating the length of each path. This is crucial when determining the critical path.
4. Use real-life examples to illustrate your understanding. This can make your answers more concrete and relatable.

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CAPM - Critical Path Method Example Questions

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Question 1

You are managing a construction project. The local government unexpectedly requires additional safety inspections that will add 3 days to both tasks B and D on the critical path. How is your project’s critical path affected?

Correct Answer: Critical path will extend by 6 days

To determine how the additional safety inspections will affect the project's critical path, we need to consider the following: 1. Identify the current critical path: The critical path is the sequence of tasks that determines the minimum time required to complete the project. Any delay in tasks on the critical path will delay the entire project. 2. Determine the impact on tasks B and D: The local government's requirement adds 3 days to both tasks B and D, which are already on the critical path. 3. Calculate the new project duration: Since tasks B and D are on the critical path, adding 3 days to each task will directly impact the total project duration. Let's assume the original critical path was A → B → C → D → E, and the durations were as follows: - Task A: 2 days - Task B: 5 days - Task C: 3 days - Task D: 4 days - Task E: 2 days The original project duration was 2 + 5 + 3 + 4 + 2 = 16 days. With the additional safety inspections: - Task B: 5 days + 3 days = 8 days - Task D: 4 days + 3 days = 7 days The new critical path remains A → B → C → D → E, but the durations are now: - Task A: 2 days - Task B: 8 days - Task C: 3 days - Task D: 7 days - Task E: 2 days The new project duration is 2 + 8 + 3 + 7 + 2 = 22 days. Therefore, the additional safety inspections will increase the project duration by 6 days (22 days - 16 days). The critical path remains the same, but the overall project duration is extended.

Question 2

In a project with tasks A (5 days), B (3 days), C (4 days), and D (6 days), where B and C can start after A, and D can start after both B and C are complete, what is the total duration of the critical path?

Correct Answer: 15 days

The correct answer is 15 days. Here's why: 1. Task A takes 5 days and must be completed first. 2. Tasks B (3 days) and C (4 days) can start after A is complete. 3. Task D (6 days) can only start after both B and C are finished. 4. The critical path is the longest sequence of tasks that must be completed in order. 5. The critical path in this case is: A (5 days) -> C (4 days) -> D (6 days) 6. Total duration: 5 + 4 + 6 = 15 days The other answers are incorrect: 18 days is too long and doesn't accurately represent the project timeline. 13 days is too short and doesn't account for all necessary tasks in the critical path. 11 days is also too short and fails to include all critical tasks in the sequence.

Question 3

In a project where Task A (5 days) and Task B (7 days) run in parallel, followed by Task C (3 days), what happens to the critical path if Task A is extended by 2 days?

Correct Answer: The critical path remains unchanged

The critical path remains unchanged in this scenario. Here's why:

1. Initially, Tasks A (5 days) and B (7 days) are parallel, followed by Task C (3 days).
2. The critical path is determined by the longest sequence of tasks.
3. Before the extension, the critical path was B (7 days) + C (3 days) = 10 days.
4. After extending Task A by 2 days, it becomes 7 days long.
5. However, Task B is still 7 days, so it remains on the critical path.
6. The total project duration is still 10 days (B + C).

The extension of Task A does not impact the overall project duration because it runs parallel to Task B, which is still longer. Task A now has 2 days of float.

Regarding the other options:
- The critical path cannot be shortened by extending a task.
- The critical path is not extended because Task B is still the longer parallel task.
- The critical path does not shift to include only Tasks A and C because Task B is still part of the longest sequence.

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