# Exam Practice - 2017 - 2019 all Exams with Solutions.pdf

Exams
Uploaded by Anna Holub 772 at 2020-06-03
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Hey hey, I hope this document will help you guys.Those are all solved Exams from June 2017 - July 2019 . Please check the comments!!I hope my answers are correct but can't promise that they are. Pls don't get confused - sometimes I gave myself points while practising and if there is a 0 it means that I gave myself 0 points but of course you can only see the corrected version :) Btw please don't mind my handwriting :)) PS: Good luck y'all for the Exam on Friday

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Can you please explain this objective function - is it correct? I don't get it how to minimze the weekend training hours, where do you see that? In the table they give. these are the hours employees from the respective company can attend the training, right? Where do you see the weekly days? If you can explain the logic of this I would really appreciate it. Thanks in advance.
The goal is to minimize the weekend training hours. Since a full training includes 3 training days we already can exclude the column for first training day from our objective function, since it is not possible to start on Saturday or Sunday. What we have left is x_i6 and x_i7, where i = the different companies and 6 and 7 = day 6 and 7 of a week (Saturday, Sunday). Now we simply include all training hours from all possible companies on training day 2 and 3 in our objective function. We need to include every company 3 times (6x_A6 = second training day on Saturday. 3x_A6 = third training day on Saturday 3x_A6 = third training day on Sunday) (credits to Max :))
Okay, thanks a lot for the fast reply. Good luck on the exam!
How did you get 8?
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LS and LF are in orange :)
Thank you so much!
Since in the final answer we include inventory cost, and that our beginning inventory is 0, shouldn't we produce 20 more somewhere?
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It would be 97,700 actually, in column 3 you took 5 x 5 avg inventory instead of 5 x 15 :)
thank you Ellie :)))
Are you sure about it because 1 additional unit would be above the allowed increase of 0.6?
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ye i mean capacity got the highest shadow price anyways, right? I don't think question expect us to even do the (23,333.33 * 0.6) calculation. but yes even with the calculation capacity will be highest
The shadow price only holds for up to an increase of 0.6 however. There is no guarantee on what the shadow price will be above that, so for all we know, it will turn negative. We would have to rerun a second sensitivity report to see for an increase of unit.
Btw this is wrong. The correct answer is x_3 + x_4 >= x_5 :)
thank you @floppy disk :)
I asked my tutor and he said there are several ways of approaching this problem but the easiest and most straight forward is the one from floppy disk so I'd use that on the exam ;)
why is 500 increase in processing no possible? is it because the company doesn't even use the full limit so there is no point in increase of 500hrs? or is there any other explanation
oh sorry my bad haha but thank you for clarifying :) yeah there is actually no sense in increasing this constraint by 500 working hours because the constraint is non-binding (so as you said correctly they don't use their full potential yet)
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on p. 38 can you pls explain e) and f)? :)
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and for question f)you look on page 48 again of the lecture slides and see if x=0 then y=0 which gives you y (then) <= x (if)
clear?
why didn't you just crash A once and G once?
because you always have to go for the cheapest option and therefore you first crash f&e (7000) < A (8500) so then you are at 20 weeks and to get to 19 you crash A because its not possible to crash f again (so there is no sense in crashing e) because you have to take into account all 3 critical paths - and that gives you a cost of 8500. but I guess your second step is that you could also crash G because it has the same crashing cost as A :)
thank you very mucho
i get that they need an ending inventory of 20 and i know how u calculated the 95000, but where did you produce the 20 endingn inventory, cause you dont hae beginning inventory and with the chase plan you only meet demand and do not have inventroy normally
it was explained in another question already :)
whoops, never mind!
how did you get to these constraints?
so in the exercise they tell you that the region wants to ensure that at least one fire station is near 15 minutes of each city. so you have to look at the table and there you see for example that from city to to city 2 it takes 10 minutes so you cover city 1 and 2 in the first constraint. then to city 5 you see in the table that city 4 is 15 min away as well as city 6 --> and the requirement is that at least one fire station is built so that gives you x_4+x_5+x_6 >= 1 . Then you do the same for the rest of the constraints. Is that clear now?
yes i think so!
could someone explaing this into more detail why this is true?
here you have to look at the table again and see that city 1,2,3,5 and 6 are are located at most 20 minutes away from city 6 . And they ask you to build at least 2 fire stations so x_1+x_2+...+x_6 >=2 for city 6
thanks!! :)
this is actually supposed to be y_11*c_11 + ... + y_66*c_66
why do you take 2/365 for the Lead Time?
I got really confused with this at first as well but it is actually quite simple - The average demand and standard deviation are given for the yearly demand. In our formula, we want to find the average demand and the standard deviation during lead time - so we divide LT/365 to find what part of the year the lead time is - the same for standard deviation. Basically you always have to bring everything in the same unit. Is that clear now?
still think its confusing, but i get it! thanks hahah
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Why didn't you answer the questions about the Hurwicz criterion? Is it not relevant?
because I didn't think it was relevant and only after uploading the document a friend told me it was - however the correct answer is in the answer key which is in the document as well :)
isn't it 50 -> so 40 liters
yes it should be 50 sorry
but the strategy is still 40 liters :)