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Backward Pass

5 minutes 5 Questions

In contrast to the forward pass, the backward pass is a project network diagram technique used to determine the late start and late finish dates of unfinished activities. It works by moving backward through the network diagram. This method helps in pinpointing the tasks that could be delayed, witho…

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CAPM - Backward Pass Example Questions

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Question 1

In a project with activities A-B-C-D-E, each taking 3 days, the project must finish in 18 days. If activity C finishes on day 9, what is the Late Start (LS) for activity E?

Correct Answer: Day 13

The correct answer is 'Day 13'. Let's break down the problem step by step: 1. The project has 5 activities (A-B-C-D-E), each taking 3 days. 2. The total project duration is 18 days. 3. Activity C finishes on day 9. To find the Late Start (LS) for activity E, we need to work backward from the project end date: 1. Activity E takes 3 days and must finish by day 18. 2. Therefore, the Late Finish (LF) for activity E is day 18. 3. The Late Start (LS) for activity E is 3 days earlier: 18 - 3 = 15. However, we need to consider the given information about activity C: 4. If C finishes on day 9, and each activity takes 3 days, activity D can start on day 10. 5. Activity D will finish on day 12 (10 + 3 - 1). 6. Activity E must start immediately after D to meet the project deadline. Therefore, the Late Start (LS) for activity E is day 13. The other answers are incorrect: - Day 15 is too late and would cause the project to exceed its 18-day limit. - Day 12 is impossible as activity D is still in progress. - Day 10 is too early, as activities C and D haven't been completed yet.

Question 2

In a project, task P (4 days), Q (3 days), R (2 days), and S (2 days) should be completed sequentially. If Q completes on the 7th day, when will S be completed?

Correct Answer: 11th day

Task Q ends on the 7th day. Therefore, Task R, which takes 2 days, would finish on the 9th day (7 days + 2 days). Subsequently, Task S, also requiring 2 days, would end on the 11th day (9 days + 2 days). So the answer '11th day' is correct. The answer '12th day' is incorrect because it adds an extra day to the project timeframe. The '10th day' answer also incorrectly assumes that Task S will be completed in just 1 day. Similarly, '9th day' is wrong as it refers to the end of Task R, not Task S.

Question 3

In a product development project, tasks are scheduled in sequence A-B-C-D. Task A has a duration of 4 days, B has 5 days, C has 3 days and D takes 2 days. The project must be completed in 14 days. If task B is completed on the 6th day, what would be the Late Start (LS) of task D?

Correct Answer: Day 12

Late Start (LS) of task D is the latest time that task D can start without delaying the project. If task B finishes on the 6th day, then task C, with a duration of 3 days, will finish on the 9th day. This means, Task D can start on the 10th day at the earliest. However, since the project must be completed in 14 days and Task D only takes 2 days, Task D can start as late as the 12th day without delaying the project. If Task D starts on the 10th day ('Day 10'), 9th day ('Day 9'), or 11th day ('Day 11'), it would either be too early or risk not finishing the project on time. Therefore, 'Day 12' is the correct answer.

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