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# D2 Pre-Exam Thread - Past Papers, Mark schemes etc Tweet

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1. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by JordanS94)
Got 69/75 on the mock paper ... It almost killed me since my printer has no ink so I had to draw everything by hand and as well as not realising there was a table for they dynamic programming ... so I made it up
I have one question about the mark scheme for the simplex method on the mock exam... Is it wrong? I took off 2 accuracy marks from the 9 because I got the profit values wrong in the x and u columns and I have no idea where they have come from It's probably just me but I am curious

And can someone gimme some tips on network flows please I keep doing my back flows wrong
I did too! But if you use the laelling procedure... literally pretend this is a completely different flow, just follow the arrows. If there is capacity in one direction (be it the opposite to the forward) go there if you need to! then compare this direction to the original, and see if you need to add or subtract the augmentation value
2. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by Zhy)
Just need to start learning simplex and the last bit of game theory now (the part that requires simplex). Doable in 1 day?
yup for simplex not sure for the game theory with simplex though ... just because I haven't learnt it since my teacher didn't even mention it to us ¬¬ But I am guessing yes because simplex and game theory are pretty simple
3. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
I did too! But if you use the laelling procedure... literally pretend this is a completely different flow, just follow the arrows. If there is capacity in one direction (be it the opposite to the forward) go there if you need to! then compare this direction to the original, and see if you need to add or subtract the augmentation value
I do that but I keep going wrong Must be me being stupid
4. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by JordanS94)
I do that but I keep going wrong Must be me being stupid
I'm the QUEEN of stupid.
5. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
I'm the QUEEN of stupid.
High 5 I bet you couldn't beat my mistake in my C1 exam x+2x =6x ... I don't even know how anyone can go so wrong it'd be normal if it was 1 off but double the answer .. :L
6. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
Easssyyy if i can, you can :P
One day to do 10 D2 papers and 16 M2 papers. It's looking bleak
7. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
Ugh, just saw the mark scheme for June 2009 Q3. Didn't think you'd lose 2 marks for not graphing the probabilities...
8. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by JordanS94)
High 5 I bet you couldn't beat my mistake in my C1 exam x+2x =6x ... I don't even know how anyone can go so wrong it'd be normal if it was 1 off but double the answer .. :L
I would bring up all my silly mistakes, but it would take a year.

9. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by Zhy)
One day to do 10 D2 papers and 16 M2 papers. It's looking bleak
I'm sure you'll be ok.
10. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
On June 2011 Q4, why have they done -3 + 6p = p? I thought you had to go 'bottom up' like it says in the textbook, which is the lowest intersection point...?
11. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by Zhy)
On June 2011 Q4, why have they done -3 + 6p = p? I thought you had to go 'bottom up' like it says in the textbook, which is the lowest intersection point...?
Not necesarily. You just shade out all the graph greater than each of the inequalities, and the highest point which is in the range is your p,v
12. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
Not necesarily. You just shade out all the graph greater than each of the inequalities, and the highest point which is in the range is your p,v
I'm confused what you mean, sorry... what inequalities? Could you explain the example on page 151 of the D2 textbook, by any chance?
13. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by Zhy)
I'm confused what you mean, sorry... what inequalities? Could you explain the example on page 151 of the D2 textbook, by any chance?
Okay so here you have 3 lines right? you shade the reigion whic is greater than each of these equations. You should only be left with all the stuff under each eqaution... so a region like a irregular pentagon. So you have the base, then a line on the left, going up with the equation 6q-7 with another line, and then the top line of the pentagon using q-4, and next side of the pentagon is the 1-5q and then another line straight down where p=1. You need to choose the vertex of this shape which has the higest V value... can you see it? Basically, the highest V value in the feasable region...
I suck at explanations..
14. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
Okay so here you have 3 lines right? you shade the reigion whic is greater than each of these equations. You should only be left with all the stuff under each eqaution... so a region like a irregular pentagon. So you have the base, then a line on the left, going up with the equation 6q-7 with another line, and then the top line of the pentagon using q-4, and next side of the pentagon is the 1-5q and then another line straight down where p=1. You need to choose the vertex of this shape which has the higest V value... can you see it? Basically, the highest V value in the feasable region...
I suck at explanations..
Thanks, I think I get it now!
15. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by Zhy)
Thanks, I think I get it now!
Are you sure you get it? It took some time for me to understand what i wrote myself :P
16. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
Are you sure you get it? It took some time for me to understand what i wrote myself :P
No it makes complete sense, the reasoning you gave works with all their other examples too! Thanks, you have saved me.

By the way, do you think the dynamic programming questions are a bit hard? For me I just see if I can spot the patterns in the table and work my way down...
17. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by Zhy)
No it makes complete sense, the reasoning you gave works with all their other examples too! Thanks, you have saved me.

By the way, do you think the dynamic programming questions are a bit hard? For me I just see if I can spot the patterns in the table and work my way down...
I prefer it if they start us off!! Then i do what you do! I dont mind doing it from a table if its not majorrly complicated. I prefer it when they give us graphs/networks to work with!

And no worrieeess!

Ps. I have a feeling minimax/maximin will come up....
18. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
I prefer it if they start us off!! Then i do what you do! I dont mind doing it from a table if its not majorrly complicated. I prefer it when they give us graphs/networks to work with!

And no worrieeess!

Ps. I have a feeling minimax/maximin will come up....
Yeah I hate it when they just give you a blank table, makes it a lot harder... just hoping the boundaries aren't stupidly high. Initially I thought this would be an easy 90+ module but now it doesn't look as simple as D1...

How many past papers are you doing? I've done most of June 2009-2011, skipping one game theory question (requires simplex), and all the simplex questions (don't know how to do them yet )... do the questions show much variety or do you think just doing a few will be enough?
19. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
(Original post by Zhy)
Yeah I hate it when they just give you a blank table, makes it a lot harder... just hoping the boundaries aren't stupidly high. Initially I thought this would be an easy 90+ module but now it doesn't look as simple as D1...

How many past papers are you doing? I've done most of June 2009-2011, skipping one game theory question (requires simplex), and all the simplex questions (don't know how to do them yet )... do the questions show much variety or do you think just doing a few will be enough?
I used to think D1 was way easier, ive changed my mind now, D2 is aiite (i dont actually talk like that)

Ive done all of the new spec papers (09 onwards) and got 70+ in all... but only just :P tbh i didnt even know D2 till Saturday, so if i can do it, i'm sure you can.

Just go through the example qs in the textbook... they cover pretty much everything.

June 2008 looks like its our spec... i'm doing it now.
20. Re: D2 Pre-Exam Thread - Past Papers, Mark schemes etc
Will someone explain to me why they added the 'U' and what it actually stands for in the the game theory come simplex question from the June 2006 Q7 please? Thanks Also, are there any more of this type of question?
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