[Cherie829]

I forgot to write prob of choosing land is 0... got that wrong before as well.
I was hoping for full mark...

This was posted from The Student Room's Android App on my GT-I9001

[michaelfiford]

Overall, quite a good paper. Went as well as could be expected. Think I may have made a few small mistakes, but nothing major.

Question 3 though, I don't know if I did something wrong, but I somehow found an optimal solution... Putting 18 through CE somehow. It's probably quite likely that I broke a rule of the stepping stone method or general transportation models, somewhere. But I did check my answer, and it seemed fine. And it made sense to be optimal, given part B.

Question 5, I didn't show there wasn't a stable solution, although reading through this thread seems to say that that's okay, giving that it was implied by the question. For part B I didn't draw it (derp?), and just made the first two equations equal (lucky systematic guess?). I'm guessing I'll lose marks for this? I didn't make it obvious that I assumed dominance over one of "Evil Dr Fiendish"'s strategies (because I didn't :P). Got the right answer at the end (lucky me?), although again, didn't state P(Land) = 0. Has it been established as to whether that's something that a mark could be lost over?

Question 6 was fine-ish. Had an argument with people after, as they were saying you couldn't augment flow through BC, as it was saturated. Glad I was right . May have lost a mark though in part E. I wanted to say max flow = min cut. I even wrote it and crossed it out. Because my "min cut" I was using the value of 2, I guess as the capacity. What I wrote, was that I could make a cut through all saturated arcs, and that BC was saturated in the desired direction, or something. Enough for 2 marks? Probably not.

Question 7 I'm not sure about. I didn't revise it, as I didn't think it was likely to come up. But after all, it's not hard given the circumstance, and makes sense within the context of itself. Just took ages to write out, costing me valuable time in Question 8. Also, after the exam someone told me it was a maximising question xD. Was v. annoyed, but glad to see it's not.

Question 8 went well. I'd actually revised this the night before (Clockmaker question anyone?). Unfortunately ran out of time. Just got the the end of stage 4/Jan, but didn't get a chance to write them out in the box at the end. M1A1 marks? :/. Also, had to rush. Had about 6 minutes for the whole question, so high chance of basic arithmetic error :/.

But yeah, good paper . GL to everyone on results day.

[WaNaBe]

(Original post by Arsey)
D2 May 2012

For question 3 part b, I got the most negative improvement index to be -3, so I'm thinking I made a very minor arithmetic error. I then went on to say it wasn't optimal etc. Will I still get the bulk of the marks - say 3/4

On 4 part c I stated that there are no negative values that appear in the profit equation/row therefore it is optimal, will that be 0/2.

[DJMayes]

(Original post by michaelfiford)
Question 5, I didn't show there wasn't a stable solution, although reading through this thread seems to say that that's okay, giving that it was implied by the question. For part B I didn't draw it (derp?), and just made the first two equations equal (lucky systematic guess?). I'm guessing I'll lose marks for this? I didn't make it obvious that I assumed dominance over one of "Evil Dr Fiendish"'s strategies (because I didn't :P). Got the right answer at the end (lucky me?), although again, didn't state P(Land) = 0. Has it been established as to whether that's something that a mark could be lost over?

A stable solution was not asked for in the question so you will not lose marks for not including it. If your method for getting to the right answer wasn't clear then you will probably lose a method mark or two - if reducing the game to 2x2 you had to show why you did that, although leaving the game as 2x3 would be perfectly acceptable. You would lose a mark for not stating that Agent Goodie should approach by land with probability 0.

Question 6 was fine-ish. Had an argument with people after, as they were saying you couldn't augment flow through BC, as it was saturated. Glad I was right . May have lost a mark though in part E. I wanted to say max flow = min cut. I even wrote it and crossed it out. Because my "min cut" I was using the value of 2, I guess as the capacity. What I wrote, was that I could make a cut through all saturated arcs, and that BC was saturated in the desired direction, or something. Enough for 2 marks? Probably not.

For 6 you needed to get a backflow through BC to end up with a final flow of 51. In order to prove this was maximal you needed to do a cut diagonally which did go through BC, but as BC was flowing the wrong way it wouldn't add any weight to the cut. You then needed to state that flow is maximal by the max flow = min cut theorem. I would say you'd probably get a mark for showing the correct cut though.

Question 7 I'm not sure about. I didn't revise it, as I didn't think it was likely to come up. But after all, it's not hard given the circumstance, and makes sense within the context of itself. Just took ages to write out, costing me valuable time in Question 8. Also, after the exam someone told me it was a maximising question xD. Was v. annoyed, but glad to see it's not.

I just had to do a double-take there and recheck the question. Don't worry me like that! :P

Question 8 went well. I'd actually revised this the night before (Clockmaker question anyone?). Unfortunately ran out of time. Just got the the end of stage 4/Jan, but didn't get a chance to write them out in the box at the end. M1A1 marks? :/. Also, had to rush. Had about 6 minutes for the whole question, so high chance of basic arithmetic error :/.

If you got the table filled out fully correctly then not writing them out in the box at the end should only lose you a couple of marks at most.

But yeah, good paper . GL to everyone on results day.

Good luck to you too

Responses in bold.

[kechg20]

I have a quick query- i got the values for the dynamic progamming table right but did each bit kinda backwards so instead of doing 3,2,1 for the action i did 1,2,3. I got 2,3,3,3 as the answer but will i lose any method marks?

Thanks

[Edwin Okli]

(Original post by kechg20)
I have a quick query- i got the values for the dynamic progamming table right but did each bit kinda backwards so instead of doing 3,2,1 for the action i did 1,2,3. I got 2,3,3,3 as the answer but will i lose any method marks?

Thanks

Probably two method marks. One for your table and one for not following the stars from the bottom of the table upwards.

[HNZ]

I think I got 61/75. Because I couldn't answer the last question. Any prediction on what UMS this could be?

[Arsey]

(Original post by HNZ)
I think I got 61/75. Because I couldn't answer the last question. Any prediction on what UMS this could be?

High B I would say


This was posted from The Student Room's iPhone/iPad App

[AAA_]

(Original post by Arsey)
D2 May 2012


Overall I think this was a fair paper. However, it did take a very long time to complete.
So I would imagine quite a few candidates will have run out of time and dropped big marks
on the linear programming question.




Q1 Allocation


Trickyish in that it was a 5x5 matrix and it weirdly went from 3 lines to 5 lines.
It also took a long time.






Q2 Salesman


V. Easy




Q3 Transportation


The first stepping stone path was weird and it was odd that it wasn't optimal; otherwise okay.




Q4 Simplex


Pretty easy but it was fraction city


I doubt many people will get part c) correct. Stating no negatives in the profit row will not be sufficent.




Q5 Game Theory


What a great question.


Fairly standard, I very much doubt many people will have reduced to a 2x2 game, using the well graph will be fine.




Q6 Flows


Pretty standard, fairly easy




Q7 Linear Programming (Allocation)


Very, very, very easy if you learnt it. It was on the 2011 paper.


4x4 was a bit mean and involved unnecessary extra writing.




Q8 Dynamic Programming


Order book... don't say you were not warned.


As order book questions go it was easy, but I still think it will be poorly answered due to candidates rushing it.








Last few June boundaries were 64, 61, 57 for 80ums


It certainly wasn't more difficult than last year so I will guess at


100ums - 75
90ums - 70
80ums - 65
70ums - 57
60ums - 50
50ums - 43
40ums - 36




This thread will be locked at somepoint and then unlocked at midnight following the Decision 2 examination. I will upload the paper and my solutions to this post.

I will do my best to answer questions about the paper but please try to read the thread first so that I am not answering the same questions lots of times.

Good luck.

In your mark scheme for Q7. you forgot 'where Xij>/0 for all values of i and j'.