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D2 6th June 2013 watch

1. still dont get it

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2. (Original post by Miken Moose)
You choose the point such that the minimum possible value of V(A) is as large as possible.

See the attached diagram -- here, we would select the intersection of the yellow and orange lines, because it gives the maximum possible minimum value of V(A), which is the vertical axis.
Thankyou!!! So as a rule, is it always the one closest to the horizontal line?

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3. (Original post by JayJay95)
Hey thats 7c not 7d take one more look for me?

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Well, Jkn has answered you above now...
4. Hi would anyone please explain June 2009 Q5 for me? I literally don't know what's going on.

And also can anyone please explain to me about this minimum cut- max flow theorem? For the flow questions the last part always ask you to prove it's maximum flow, but then I am confused on how to and where to draw the cuts, if there are so many saturated edges after the max flow algorithm.
5. (Original post by Miken Moose)
Well I do it like that because it makes sense, but if you look at January 2006 question 3, they allowed either equalities or inequalities for those constraints.
Yeah, that's why I do it, too. In fact, that's why I chose maths in the first place - things make sense. That's also why I hate Decision Maths - most of it makes sense but some of it isn't even explained.
6. (Original post by kashagupta)
Thankyou!!! So as a rule, is it always the one closest to the horizontal line?

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Well... usually, but that's not really the 'point' (if you'll excuse the pun).

If you look at that diagram again, and look at the intersection of, say, the red and orange line. The reason we don't pick this is because, at that particular value of p, the minimum value of V(A) is much lower - from the yellow line. Notice how there are no lines below the intersection of the orange and yellow lines.

I hope this helps - it's kind of hard to explain, maybe someone else can do it better.
7. (Original post by Miken Moose)

Well, Jkn has answered you above now...
Yeah but i dont get his explanation at all

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8. (Original post by JayJay95)
still dont get it

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Okay, I would think it would go like this:

Stage = product he is considering allocating units of milk to (i.e. Butter, cheese or yoghurt)
State = number of units left to allocate at this stage
Action = number of units allocated to this product
Destination = the number of units remaining after allocation

Note that there is a very similar example on page 221 of the textbook.
9. (Original post by Miken Moose)
Okay, I would think it would go like this:

Stage = product he is considering allocating units of milk to (i.e. Butter, cheese or yoghurt)
State = number of units left to allocate at this stage
Action = number of units allocated to this product
Destination = the number of units remaining after allocation

Note that there is a very similar example on page 221 of the textbook.
Ohhhh thanks a lot makes sense cant believe i couldnt get that!

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10. (Original post by Jkn)
How are people feeling about tomorrow then? Psyched?

I'm looking forward to it in the sense that it is my first maths exam this summer (finally my English, Spanish, etc.. are over!)
Well, it's probably my easiest exam this Summer, so hopefully will be a nice smooth start with nothing going wrong whatsoever...
11. (Original post by Jkn)
Add a dummy to transform it into a problem in the correct form and then continue as usual (slack variables/inequalities, etc...)

Consider, instead of a time parameter underlying the action, the parameter of quantity left. How much milk will you have left after a creation action deeding on what it is etc...

Of the points of intersection that lie on the border of the feasible region, you must select the point that co-ordinates to the highest expected value. The feasible region is such that all co-ordinates in the region satisfy and are less than or equal to every line drawn.

How are people feeling about tomorrow then? Psyched?

I'm looking forward to it in the sense that it is my first maths exam this summer (finally my English, Spanish, etc.. are over!)
This is my first exam, but then I have another two weeks until my others. I think I'm either going to do very well or very badly. I need to try not to make mistakes on the transportation problems (and the others as well ). Because yesterday I was doing a transportation problem question, and I realised that I had used costs when I was meant to use stock. So I crossed out the table and redrew it and then did the same thing again . I know that I'm going to have to end up asking for extra paper and drawing some tables myself because I'll make too many mistakes.
12. Part C only: I thought you would increase blending because there is slack available?? why does mark scheme say opposite??
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13. (Original post by Miken Moose)
Well, it's probably my easiest exam this Summer, so hopefully will be a nice smooth start with nothing going wrong whatsoever...
(Original post by brittanna)
This is my first exam, but then I have another two weeks until my others. I think I'm either going to do very well or very badly. I need to try not to make mistakes on the transportation problems (and the others as well ). Because yesterday I was doing a transportation problem question, and I realised that I had used costs when I was meant to use stock. So I crossed out the table and redrew it and then did the same thing again . I know that I'm going to have to end up asking for extra paper and drawing some tables myself because I'll make too many mistakes.
Mine too, with the possible exception of S4

Are you doing M4, M5, STEP etc... ? (where **** gets real ) Urgh yeah sounds like the kind of stuff I've been doing in general! I learnt D2 in the space of a sunday afternoon so I'm now going over it again and planning on doing June 2011 and 2012 tonight

How have you guys been doing on mocks so far then?
14. (Original post by JayJay95)
Hey arsey,

Was wondering if you had any tips for labelling the stage, state, action and destination in a DP question

Also in transportation, does a degenerate solution only occur when demand and supply are met in a single cell?

On a side note, are you also going to be posting an unoffical markscheme for M2?

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1. try and start the question as it should then help you work out what they are.

2. no, it can also occur following the stepping stone, which happened on the June 11 paper (I think)

3. yes
15. (Original post by imasha.sj)
probably, there were quite a few errors on the mock paper.
16. (Original post by Jkn)
Mine too, with the possible exception of S4

Are you doing M4, M5, STEP etc... ? (where **** gets real ) Urgh yeah sounds like the kind of stuff I've been doing in general! I learnt D2 in the space of a sunday afternoon so I'm now going over it again and planning on doing June 2011 and 2012 tonight

How have you guys been doing on mocks so far then?
Yeah I'm doing D2, M3-5 and S3-4. Fun stuff S4 is easy? I find it quite hard to not fall asleep to.
17. Hi, after reading this thread I'm confused whether in a normal transportation linear programming equality or inequality is used for the constraints?
18. Could someone confirm the following please?

For transportation problems it'll only ever be maximise

We will only have to maximise a linear programming problem

Allocation can be maximise or minimise

Game theory LP will only be maximise

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19. (Original post by Jkn)
Mine too, with the possible exception of S4

Are you doing M4, M5, STEP etc... ? (where **** gets real ) Urgh yeah sounds like the kind of stuff I've been doing in general! I learnt D2 in the space of a sunday afternoon so I'm now going over it again and planning on doing June 2011 and 2012 tonight

How have you guys been doing on mocks so far then?
I'm doing STEP I and AEA. I've been too scared to do any mechanics beyond M2 . In mocks, my marks seem to range from around 60 to 75. The only problem is that it already takes me long enough to complete a paper (damn you Simplex ) so I can't really afford to spend much longer on the questions than I already do, especially if I need to take into account table drawing time! It took me a lot longer than a Sunday afternoon to learn this . Do you need a decent grade in this, or are you just doing it to get the additional further maths qualification?
20. (Original post by Matt_payne)
Hi, after reading this thread I'm confused whether in a normal transportation linear programming equality or inequality is used for the constraints?
If the problem is balanced (i.e. total supply = total demand), then the constraints should be equalities. This is because all of the demand must be met, you cannot have less delivered than what is demanded.

Additionally, since all demand will be met, this means that all supply will have to be used (remember that in a balanced problem, total supply = total demand). Therefore these constraints should be equalities too.

The only case when you should have inequalities is when you have an unbalanced problem (total supply > total demand). In this case, the total demand must still be met and so these constraints should still be equalities. However, since there is more supply than what is needed, the supply from each depot will not necessarily be used up so these should be inequalities.

I hope this clears it up for you

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