newbie looking for answers on scheduling questions 2

[dav1dd]

Greetings all;

I'm preparing for the PMP and I found a really good test bank at

http://www.oliverlehmann.com/pmp-self-test/75-free-questions.htm.

(No, this is not an advertisement – I’m really looking for help here.)

I did well on the practice test, but flubbed some scheduling questions. I’m looking for expert advice on how to determine the correct answers to these questions (#31 = B, & #32 = D).

Anyway, thanks in advance for your help.

Dave.

 

[PDQBach]

Without telling us why you chose an answer, it's a bit difficult to explain where you went wrong. It would have helped, too, if you had simply given the answer you chose so you could be shown why it was the wrong answer. The two questions are not particularly difficult and reflect the level of difficulty you should expect on the test. (Yes, I have my PMP.)

Here's what I did:
Question 31. There are two areas for potential error.

Activity 3. The notation "FF-2 days" means that Activity 2 will finish 2 days after Activity 3 finishes. (For the purists reading this: I know, that's not technically correct but it will do here.)

Activity 4. The notation "FS+3days" means that Activity 4 will start 3 days after Activity 3 finishes.

Task1: Duration 20d; no linkage; no lag
Start = day1
Finish = Start + Duration-1 = day1 + 20-1 = day20

Task2: Duration 10d; FS linkage; no lag
Start = day after predecessor ended = day20 + 1 = day21
Finish = Start + Duration-1 = day21 + 10-1 = day30

Task3: Duration 5d; FF linkage; negative 2d lag
Finish = day predecessor ended plus lag = day30 plus lag = day30 plus (-2) = day28
Start = Finish - Duration-1 = Day28 - 5-1 = day24

Task4: Duration 6d; FS linkage; positive 3d lag
Start = day after predecessor ended plus lag = day29 plus lag = day29 plus (3) = day32

Question 32.
This is quite straightforward and I cannot guess where you went wrong. Perhaps you didn't have both taskA and taskE starting at the beginning of the schedule.

 

[dav1dd]

PDQBach - thank you for replying to my question and letting me know how to work the FF-2 / FS+3 question.

Most of my work is pretty straight forward as far as scheduling goes (strictly FS with very few if any, leads/lags) so this all pretty new to me. (BTW, my answer to this question was 42.)

I'm still looking at the ADM question but fail to see the simplicity of it. (My answer to this question was 34.) Care to illuminate the path for a dim bulb like myself?

 

[PDQBach]

I quickly sketched it as a Gantt chart.

Remember that the dotted line is an implied predecessor/successor relationship (there's a proper term for the delay but I can't remember it off-hand) so:

B and E must both finish before C can start. Or, reading backwards, C can start only when both B and E are finished.
B and G must both finish before H can start. Or, reading backwards, H can start only when both B and G are finished.

A starts on day1
E starts on day1

When your chart is done:
A starts day1
B starts day15
C starts day23
D starts day29
E starts day1
F starts day23
G starts day31
H starts day38

Add Duration-1 to the start dates to get the finish dates.

 

[dav1dd]

PDQBach - in my earlier post I called myself a dim bulb; is there something dimmer than dim? Off?

After reading your notes I realized why I couldn't figure this one out. The reason is, is because for task F, I used a duration of 22 v. a duration of 8. I failed to RTFQ.

Besides showing me how poorly I read questions, your post also showed me the proper way to run the numbers. I would have simply added the durations for the longest path (22+8+7+12=49) and used that as the answer. You showed me some things I need to think about before I run off and answer blindly.

Thanks again for your help and patience.

 

[PDQBach]

Glad I could be of some help. Good luck when you write the exam!