I had to sort for hours through hours of videos from people who barely speak any English and did not know how to explain crashing correctly. Thank you for posting this! this truly helped me. The inclusion of indirect cost is totally needed in crashing.
Hey thanks for letting me know. I have seen other examples that don't include indirect costs and think it's a shame to leave out. Feel free to check out the rest of my PM videos if you haven't already at engineer4free.com/project-management this is video # 29 of 46. Cheers!
omg thank you!!!! this just saved me on my project management exam thank you so much for your amazing explanation it definitely makes sense to me now! you've literally saved me, had to subscribe!
Amazing, thanks for letting me know! Do check out all the PM videos that I made here: engineer4free.com/project-management if you haven't already, and share them with some classmates 😊
Thank you for taking the time to create these videos.. this material is hard for me to digest because I am not process oriented, I am task oriented having left IT years ago BUT my current role requires this soooo.. thank goodness for this video..
You can do it! Sounds like you know already that there are more videos here: engineer4free.com/project-management but thanks for being subscribed and watching! =)
Hey, great videos! You have been of great help for more than two years for me now. Okay, in the 3rd run, you saved a day each from activity C & D, aren't those supposed to be 2 days and the total cost equivalent to $1200? Perhaps since you crashed on the same day got me confused.
Heyyyy that's awesome to hear! Glad I can help and that you've stuck around so long =) =). Now to answer your question. At the beginning of run 4, there are two critical path: A-B-C-E and A-B-D-E. each path before the 4th run is 15 days long. If you crash A-B-C-E, then A-B-C-E would have 14 days of activity and 1 day of float, while A-B-D-E would still be 15 days of activity, so the project duration would still be 15 days. So, to actually shave a full day off the project and get the whole project down to 14 days, we need to also crash A-B-D-E. Once we do this, A-B-C-E and A-B-D-E will both have 14 days long, and will both be critical again. So, we have crashed twice, but only reduced the entire project duration by one day (from 15 days to 14 days). Our whole project costs us $600 per day in overhead, and because we have only shaved off one day (15 days down to 14 days) we have only saved one day in in overhead costs. Really I should have crashed A-B-C-E and A-B-D-E in two separate steps to show that the project duration wouldn't be affected with only one of them crashed, but I just wanted to speed it up a bit so I did both together. Does that make sense?
@@Engineer4Free It makes sense now... thank you so much! And thank you for the timely response, I am working on my assignment, the timing was perfect. Keep doing what you do. How I wish you were my professor... straight A's lol.
Appreciate the demonstration, but, if I am not wrong, there are a few mistakes. The TF in Run 2 should be 0 on B and 1 on C. Also, the duration D in Run 3 should be 5 as the Days Saved is 2.
ive watched most of you PM vids, they are sooo helpful! thank you so much. this one, though, was a bit confusing. i think it wouldve been better if you took more time explaining each step. otherwise thank you so much!
Hey Tima, there was a video that I did that explains the process of project crashing, and then this two part example. If you haven't seen the explainer vid yet, it's here: www.engineer4free.com/4/project-crashing-explained If you had already seen it and still find crashing a bit difficult, that's normal. There's a lot going on in these problems and it just takes some practice to really become comfortable with knowing that you are making the right decision at each step =)
Thanks a lot! these videos are awesome! keep it up :) btw there is another typo in this part as well, at 5:43 you say 1,100 but write 11,000. I thought I should point that out.
Hi, don't you think on the run 2, the cost should be 500 + 600? Because on run 2, you crash activity E and B. In you calculation you only count the crash cost of activity B.
That sounds terrible. Probably not. You want to iterate until the project can't get any shorter. With 5 critical paths, there's probably a trick in your problem that will make it so that you only actually have a crash a few times.
Kindly explain why in Run 4 Activity C & Activity D were crashed simultaneously? Agreed they are both on the critical path, but the same situation happened in Runs 1 - 3 and you only crashed the activity having the least additional cost/day.
Always crash one day at a time. You need to find the ES,EF,LS,LF of all impacted activities (which can be many) every time you crash one activity by one day. If you skip this and try to do two days at once, you'll start getting incorrect results.
Hey @engineer4free , Great content and super helpful. Just one question though. Why did you not just crash one of the variables at 3:55 ? I know you said it is becuase "they are in parallel" but im not sure what this means. Could you elaborate? thanks.
Since both the activities are now critical, we need to crash both in-order to reduce the project duration, if we crash only one like u said there will be no impact on project duration (i.e., project duration does not reduce) For better understanding - Imagine a building resting on 2 columns whos height is 30m (I know building with 2 columns doesn't exists but lets imagine) so in-order to reduce the building height we need to remove 2 columns, if only 1 column is removed the building height does not change. Plz correct me if am wrong.
In this problem, the "Normal Cost of Activity" does not change if the activity is shortened. I prioritize based on "Additional Cost/day to Crash" for activities on the critical path. Following this, Activity E was the best choice, so it gets crashed first.
@@tariqfarooq543 Thank you for the answer. I'm not a PM now, but I became an industrial engineer 😂 This video was very useful for the exam. Good luck bro!
I cant remember if I have an example with that condition. All of the videos are here: engineer4free.com/project-management If you have two initial activities with no predecessors, just start them both with ES = 0 (or ES = 1 if that's the system you use) an then proceed with the forward and backward pass. When you get back to the beginning, at least one of those initial activities must have a LS = ES, but the rest don't necessarily need to.
Hi! Can you clarify why we have to crash C&D together for Run 5? Is it because C is now also on a Critical Path or is there any other factors playing into this? Thanks !
If you only crash one of them you will not reduce the whole project duration because the other task that you don't crash will remain on the critical path with the same number of days. So yes, that's the only reason why he crashes both together.
If you crash an activity that is not on the critical path, it will not reduce the project duration which will likely defeat the purpose of crashing. Sometimes you sort of need to do this though, like in the event that there are two parallel critical paths.
So in the exercise i have to do we are given months instead of days and the crash cost doesn't specify if it is the overall, per day or per month.... should i still calculate on per month basis??
Yeah I would think so. The "time-unit" in these problems can be days, weeks, months, or years, etc, but regardless the process is the same. All costs in network diagram problems will typically be given per "time-unit" or per activity, and crashing is per "time-unit" so I would think it's safe to assume that if your problems says something to the effect of "the crash cost of activity A = $1000" then it costs $1000 to crash it by a month.
Hey thanks for commenting! It's a little hard to see cause there's so much congestion and different colors and the red 12 is crossed out with a lighter purple that's hard to see, but for C the LF is 11 and the EF after that last crash is 10. 11-10=1. Or alternatively, LS-ES=7-6=1. Does that clear it up?
+Arvind Reddy Hey no, run 4 reduces the total project duration by 1 day only (from 15 days to 14 days). We do shorten Activity C by 1 day and also Activity D by 1 day, but it's actually the same day because in run 4 they are both on the critical path. Hope that helps! Also I noticed that I wrote 11,000 instead of 1,100 for the cost of run 4 even when I correctly say its 1,100, sorry if that caused any confusion too!
you are interpreting it a bit wrong, "days saved" are actually "days saved for the whole project" and not for each activity. in this case we are actually saving only 1 day for the project = 600.
