Thanks I cearly understand how to crashing a project. In fact, I think you teach better than my school's professer even English is not my mother tongue haha. Well teaching !!!!!
Its very well defined. One question. While crashing you need to prioritise by longest path first, 4:50 but after that we need to prioritise either the burst/merge node or simple node. Here answer would be same but still for other problems it may differ.
I have an example from my homework that is throwing me off. For activity D, the normal duration is 1 (day) and the crash is 3 (days). if I take the crash and subtract the normal duration I get -2 which doesn't seem right. Any advice on how to do that properly? All the rest of the activities have the crash duration smaller than the normal duration.
Hi, if there was a scenario that at the end of crashing A-D-G and B-E-G paths (where both = 9 weeks) were you to find that the C-F path also contains 9 weeks (in which case all 3 paths are now critical paths), how would you go about it? Will you now reduce F as well as reduce E (from the B-E-G path) or is that not possible? Thanks
If the critical paths are all 9 weeks, if you had the ability to crash activities you would have to crash an activity on EACH path so they all get reduced. You can’t crash F by one week (making C-F 8 weeks) and leave ADG and BEG at 9 weeks. The challenge is to be able to balance all of the critical paths. Hope this helps.
Hello Jyoti, You have be very careful with crashing. You would concentrate on the lest expensive crash cost that is ON the critical path (i.e. The path with zero slack). As you crash activities, the critical paths will change (you might end up with multiple critical paths) and you might have to move to a different path to find the next viable activity to crash. Ideally, you can crash a single activity that is on multiple critical paths. Crashing an activity just because it is the least expensive but isn't on the critical path is a waste of money because it won't reduce the project completion time. Hope this helps. Mark
A can be crashed by only 1 week (from 4 to 3). After that, there are two critical paths, so even if you crash E, you can't crash the path with A any more so you would be wasting your money to crash E.
Hi there. If you go to 8:20 in the video, you can see that G is crashed by 2 weeks getting down to 10 weeks. If you're asking why it wasn't crashed earlier, that's because D was less expensive. Hope this helps. Mark
Hi John, While we could crash activities B and E they won't reduce the total project time because we would have to also crash an activity along path A-D-G and all of those activities have already been crashed to as low as they can go. Spending money on B and/or E would be a waste because while the time on path B-E-G could be reduced, A-D-G would still be at 9 weeks. Hope this helps. Mark
Hi there. At some point you can end up with more than one critical path, so when you crash A, that reduced the time along A-D-G, but then B-E-G must also be reduced. You might be thinking of the part in the video where just before I take the time of B-E-G I took 1 off A-D-G -- that's because I missed updating my little crash table. Hope this helps. Mark
Hi sir, may i ask - how do we get the Crash Time Values (in column 2) ? Also must the Duration Unit be standardized to weeks? or can it be any other time unit (i.e. man-days)?
Hi there. The crash time values are provided, so there are no calculations required. You can use any unit you like: days, weeks, months, etc.. Hope this helps. Mark
Hi Maram, If you look at the summary at around 10:00 in the video, you'll see that after crashing to 7 weeks, both paths A-D-G and B-E-G are critical at 9 weeks. While you could spend money to crash B and E and get below 9 weeks you would be wasting the money because you cannot crash any more on A-D-G so it would still be 9 weeks. At this point you have more than one critical path and to be able to continue crashing, you must be able to crash activities on both paths otherwise you cannot proceed. Hope this helps. Mark
Hi Joud. This is because at some point there is more than 1 critical path and to reduce the time by one week either 1 task that is common to both paths must be crashed or 1 task on each path must be crashed. In this case if you crashes A only that path would be reduced by one week but the path E is on will not. Hope this helps Mark
@@kathestrella-ju8bc If you crash E by more than 1 week without crashing another activity an a different path, you would be wasting your money because the project time will not be reduced. Hope this helps.
Hi Olo, You can't go any further because the remaining activities that could still be crashed are not on the critical path. So you COULD pay money to complete them in a shorter time period, but it won't reduce the total project time, so you would be wasting your money. A valid reason for paying extra to free up the resources to complete those activities earlier might be to allocate the resources to another project. Hope this helps. Mark
Hi there, The textbook for that one is: Operations Management: Sustainability and Supply Chain Management, Third Canadian Edition by Hweizer, Render, Munson, and Griffin ISBN 978-0-13-483807-6 Hope this helps. Mark
If you crash D the project time will not be reduced because at least one other path is still critical. You have to crash activities on each critical path by the same amount for the project time to reduce. We try to crash activities that are common to multiple critical paths to save crash cost but that’s not always possible.
Wait a second: 4:05 The critical path is ADG? But you only did the forward pass, didn't you? Is that sufficient enough to determine the critical path? What about the backward pass?
You only need to do a forward pass as long as you go through all the paths. The longest path is the critical path. You really only need to the the backward pass to determine what the slack for an activity is. All activities in the critical path will have zero slack but the other ones need the backward pass to determine the slack. Hope this helps!
Just because an activity can continue to be crashed doesn’t make it should be because there can be other critical paths that have to be balanced so continuing to crash A and E won’t reduce the project time any further. You must carefully observe when other paths become critical and then try to crash activities line on all the path risk or find activities on each path that can be crashed by the same time to keep the path times balanced.
Hello Sir, So do you mean that every time we crash separate activities when we have 2 critical paths like we did for E and A we just crash once for both because in this case we had crash time limit of 3 weeks which we could do for both A and E to leave us with 7 not 9 weeks but we just crashed 1 week not 3
![โจทย์โหดเหมือนโกรธเป็ดถีบ [อะไรอยู่บนหัวกูวะ ... EP.4]](http://i.ytimg.com/vi/Dqlb7EZ9PGk/mqdefault.jpg)
This went hand in hand with a homework problem I was struggling with. Thank you for your detailed explanation!
You’re very welcome!
I just watched this well explained video. Step by step solution to the end was very interesting.
Thanks!!
Thanks I cearly understand how to crashing a project. In fact, I think you teach better than my school's professer even English is not my mother tongue haha. Well teaching !!!!!
Thank you very much for the kind words! I’m glad it helped you.
one would think crashing a project would be a bad thing :))
@@aronkovacs9604 One would think!
I really need this because online classes and these charts and the DNA strand map .... I hate how lost I can be.
I’m glad they are helpful to you.
Very well done.
Thank you! If you haven’t already, please consider subscribing!
Its very well defined. One question. While crashing you need to prioritise by longest path first, 4:50 but after that we need to prioritise either the burst/merge node or simple node. Here answer would be same but still for other problems it may differ.
Yes, depending on the problem and parameters there can be more than one combination of crashing activities
Helal olsun kardeşim sana sayende dersi gecicem
You’re welcome!
I have an example from my homework that is throwing me off. For activity D, the normal duration is 1 (day) and the crash is 3 (days). if I take the crash and subtract the normal duration I get -2 which doesn't seem right. Any advice on how to do that properly? All the rest of the activities have the crash duration smaller than the normal duration.
Hi David,
Well that is an interesting one. I suspect it might be a typo. I suggest you confirm with your instructor on that one.
Mark
Hi,
if there was a scenario that at the end of crashing A-D-G and B-E-G paths (where both = 9 weeks) were you to find that the C-F path also contains 9 weeks (in which case all 3 paths are now critical paths), how would you go about it? Will you now reduce F as well as reduce E (from the B-E-G path) or is that not possible? Thanks
If the critical paths are all 9 weeks, if you had the ability to crash activities you would have to crash an activity on EACH path so they all get reduced. You can’t crash F by one week (making C-F 8 weeks) and leave ADG and BEG at 9 weeks. The challenge is to be able to balance all of the critical paths.
Hope this helps.
when crashing a project do we have to concentrate on task with least expensive gradient or path with least slack?
Hello Jyoti,
You have be very careful with crashing. You would concentrate on the lest expensive crash cost that is ON the critical path (i.e. The path with zero slack). As you crash activities, the critical paths will change (you might end up with multiple critical paths) and you might have to move to a different path to find the next viable activity to crash. Ideally, you can crash a single activity that is on multiple critical paths.
Crashing an activity just because it is the least expensive but isn't on the critical path is a waste of money because it won't reduce the project completion time.
Hope this helps.
Mark
Well explained, thank you
You’re welcome!
Very well explained
Thanks very much!
Thank you for the explanation. Just One question. Why don't we crash A and E further ? we only consider A and E's crash week as 1
A can be crashed by only 1 week (from 4 to 3). After that, there are two critical paths, so even if you crash E, you can't crash the path with A any more so you would be wasting your money to crash E.
When crashing G, if the max crash for G is 2 weeks, why aren’t we subtracting 1 week from each critical path to get a 11 week critical path?
Hi there. If you go to 8:20 in the video, you can see that G is crashed by 2 weeks getting down to 10 weeks. If you're asking why it wasn't crashed earlier, that's because D was less expensive.
Hope this helps.
Mark
why dont we further crash B and E? was it because originally the critical path was ADG?
Hi John,
While we could crash activities B and E they won't reduce the total project time because we would have to also crash an activity along path A-D-G and all of those activities have already been crashed to as low as they can go. Spending money on B and/or E would be a waste because while the time on path B-E-G could be reduced, A-D-G would still be at 9 weeks.
Hope this helps.
Mark
Hello sir, one question. When you crash E by 1 week, why you also minus the ADG path because theres no E in that path.
Hi there. At some point you can end up with more than one critical path, so when you crash A, that reduced the time along A-D-G, but then B-E-G must also be reduced. You might be thinking of the part in the video where just before I take the time of B-E-G I took 1 off A-D-G -- that's because I missed updating my little crash table. Hope this helps.
Mark
Thank you so much
You’re welcome!
Hello sir. I have a question, the difference between normal time and crash time is the counts of crash?
Yes. If the normal time is 10 days and the crash time is 8 days then the activity can be crashed by 2 days
Hi sir, may i ask - how do we get the Crash Time Values (in column 2) ?
Also must the Duration Unit be standardized to weeks? or can it be any other time unit (i.e. man-days)?
Hi there. The crash time values are provided, so there are no calculations required. You can use any unit you like: days, weeks, months, etc..
Hope this helps.
Mark
why can't we crash more of B and E I don't clearly understand the reason ?
Hi Maram,
If you look at the summary at around 10:00 in the video, you'll see that after crashing to 7 weeks, both paths A-D-G and B-E-G are critical at 9 weeks. While you could spend money to crash B and E and get below 9 weeks you would be wasting the money because you cannot crash any more on A-D-G so it would still be 9 weeks. At this point you have more than one critical path and to be able to continue crashing, you must be able to crash activities on both paths otherwise you cannot proceed.
Hope this helps.
Mark
Could you tell me the name of the book please?
The textbook for that course was Heizer, J., Render, B., Munson, C., & Griffin, P. (2020) Operations Management (3rd Canadian edition)
thanks bro
You're welcome, Zain! If you like the videos, please consider subscribing!
why are the last two crashings for A and E considered 1 week together?
Hi Joud. This is because at some point there is more than 1 critical path and to reduce the time by one week either 1 task that is common to both paths must be crashed or 1 task on each path must be crashed. In this case if you crashes A only that path would be reduced by one week but the path E is on will not.
Hope this helps
Mark
@@The_Business_Doctor why isn't E multiplied by 3 weeks?
@@kathestrella-ju8bc If you crash E by more than 1 week without crashing another activity an a different path, you would be wasting your money because the project time will not be reduced. Hope this helps.
why we stop at 7 weeks and why did not go further why dont you tried to reduce E or B more
Hi Olo,
You can't go any further because the remaining activities that could still be crashed are not on the critical path. So you COULD pay money to complete them in a shorter time period, but it won't reduce the total project time, so you would be wasting your money. A valid reason for paying extra to free up the resources to complete those activities earlier might be to allocate the resources to another project.
Hope this helps.
Mark
hi may i know the textbook you refer for the exercise. thanks!
Hi there,
The textbook for that one is:
Operations Management: Sustainability and Supply Chain Management, Third Canadian Edition by Hweizer, Render, Munson, and Griffin ISBN 978-0-13-483807-6
Hope this helps.
Mark
Why are we crashing D by just 1 week when we can crash it by 4 weeks?
If you crash D the project time will not be reduced because at least one other path is still critical. You have to crash activities on each critical path by the same amount for the project time to reduce. We try to crash activities that are common to multiple critical paths to save crash cost but that’s not always possible.
Wait a second:
4:05
The critical path is ADG?
But you only did the forward pass, didn't you? Is that sufficient enough to determine the critical path?
What about the backward pass?
You only need to do a forward pass as long as you go through all the paths. The longest path is the critical path. You really only need to the the backward pass to determine what the slack for an activity is. All activities in the critical path will have zero slack but the other ones need the backward pass to determine the slack.
Hope this helps!
column 6, 2nd difference is incorrect though, right?
Hi there. Yes there is a typo there. Someone else had noted that before in a previous post which I confirmed. It doesn’t change the answer, however.
@@The_Business_Doctor super 💯
Why activity A and activity E can only reduced by 1 weeks, but both activities have crash time limits up to 3 weeks
Just because an activity can continue to be crashed doesn’t make it should be because there can be other critical paths that have to be balanced so continuing to crash A and E won’t reduce the project time any further. You must carefully observe when other paths become critical and then try to crash activities line on all the path risk or find activities on each path that can be crashed by the same time to keep the path times balanced.
Hello Sir, So do you mean that every time we crash separate activities when we have 2 critical paths like we did for E and A we just crash once for both because in this case we had crash time limit of 3 weeks which we could do for both A and E to leave us with 7 not 9 weeks but we just crashed 1 week not 3
Hi! I would like some help in a project management problem. Can i send it via email?
Sorry, I wish I could but I’m at my maximum capacity right now.
i think max crash is 8 weeks not 7 weeks
because total max crash is $1600
Hi Riska, the maximum this project can be crashed is by 7 weeks to end up at a 9 week project time. The solution is correct.
Mark
@@The_Business_Doctor Hello sir, can you explain why (in detail)? I'm so sorry, I'm still a little bit confused. Thank you in advance
I still think your speed is way too fast
You can slow it down
why the monkey bits is this called Crashing? :/
Good question! We'll have to ask the Project Management Gods about that one.
Kindly drop your email, please. I need help with project management activities.
Hi Sabelo, you are free to email me at mark@strategema.ca to let me know what you are looking for.