x Turn on thread page Beta
 You are Here: Home >< Maths

# D2 6th June 2013 watch

1. (Original post by Lilmzbest)
Oh...hmm i shall have to go trawling through old papers to try and find one of these questions, can't find any in the book

...Am i being stupid because i can't even get my head around how that would work?
It's actually easier than maximising or minimising.

Do you have the new textbook? Pretty sure it's there - not sure where else I'd have learnt if from.
2. Might sound like a stupid idea but could everyone just post the stupid errors they've been making. That way we can all learn to be conscious of where we're likely to go wrong and hence reduce the likelihood of actually making a mistake.

For me I always screw up on: using the wrong table to calculate the shadow costs; mixing backflow with forward flow when using the labeling procedure; and SIMPLEX!
3. (Original post by knowledgecorruptz)
Might sound like a stupid idea but could everyone just post the stupid errors they've been making. That way we can all learn to be conscious of where we're likely to go wrong and hence reduce the likelihood of actually making a mistake.

For me I always screw up on: using the wrong table to calculate the shadow costs; mixing backflow with forward flow when using the labeling procedure; and SIMPLEX!
Good idea!

-Forgetting to reduce columns in the Hungarian algorithm. I don't know if it is just me, but I forget this so many times and it is so frustrating.

-To find the value of a game, sub p back into one of the equations you used to calculate it, and not just any equation, like the unused one. To check, put it in the other equation you used and it should give the same value.

-Always read if it is maximising or minimising hungarian.

-Remember to give answers in real terms. If the question says at the start, here are costs in £'000s, make sure you multiply your final answer by 1000.

These aren't mistakes I've made per se, but just things to look out for

That's all for now
4. (Original post by knowledgecorruptz)
It's actually easier than maximising or minimising.

Do you have the new textbook? Pretty sure it's there - not sure where else I'd have learnt if from.
Yeah thanks i had another look last night and found in the new textbook, lol i just hadn't done any questions like that in past papers so had forgotten about it
5. I have attached both question and mark scheme, can someone check if the mark scheme is correct for me? for arc D-I on the labelling procedure, should the backwards arrow be 16????
Attached Images

6. (Original post by Knoyle quiah)
I have attached both question and mark scheme, can someone check if the mark scheme is correct for me? for arc D-I on the labelling procedure, should the backwards arrow be 16????
Yep, looks like a typo. Man, the resources for this exam are so poor.
7. How does everyone find max flow=min cut?? it takes me soo long by doing trial and error of possible cuts, does it take people long normally?
8. Does the mark scheme mean give an example of something , or literally write what the mark scheme says??? also what is an example?
have attached qsn and ms
Attached Images

9. (Original post by Knoyle quiah)
How does everyone find max flow=min cut?? it takes me soo long by doing trial and error of possible cuts, does it take people long normally?
Trial and error? The min. cut should go through the fully capacitated arcs in your network, and only the fully capacitated arcs.
10. (Original post by knowledgecorruptz)
Might sound like a stupid idea but could everyone just post the stupid errors they've been making. That way we can all learn to be conscious of where we're likely to go wrong and hence reduce the likelihood of actually making a mistake.

For me I always screw up on: using the wrong table to calculate the shadow costs; mixing backflow with forward flow when using the labeling procedure; and SIMPLEX!
Yeah, on transportation problems, I always use shadow costs when working out a new route (using theta values). It's so annoying. An I've usually wasted about three tables before I notice I've done it wrong! If we do run out of tables, is there anyway for us to get new tables or do we have to draw them out ourselves on spare paper?

Also, with Hungarian, I usually just ignore the question and start answering it, so whenever it's a maximise question, I often get it wrong. I need to stop being so lazy and actually read the full question .
11. (Original post by brittanna)
Yeah, on transportation problems, I always use shadow costs when working out a new route (using theta values). It's so annoying. An I've usually wasted about three tables before I notice I've done it wrong! If we do run out of tables, is there anyway for us to get new tables or do we have to draw them out ourselves on spare paper?

Also, with Hungarian, I usually just ignore the question and start answering it, so whenever it's a maximise question, I often get it wrong. I need to stop being so lazy and actually read the full question .
I know, I'm quite worried about that, too. Don't really fancy drawing out my own tables. Especially for simplex!
12. (Original post by knowledgecorruptz)
I know, I'm quite worried about that, too. Don't really fancy drawing out my own tables. Especially for simplex!
And I do simplex the slow way, so I'd have to draw out twice as many tables!
13. How do i even attempt question C???????????
Attached Images

14. What is the value of cut C1??? mark scheme says different to me
Attached Images

15. (Original post by Knoyle quiah)
What is the value of cut C1??? mark scheme says different to me
cut1 - 83
Smith
16. (Original post by smith50)
cut1 - 83
Smith
Thats what i thought but mark scheme says 103, error in mark scheme??? they have included that arc leaving the cut for some reason of value 20
17. Finally returned to the Edexcel past papers. Easy 71/75 on June 2012 I think it was just the odd format of the practice papers that was putting me off.
18. (Original post by knowledgecorruptz)
Finally returned to the Edexcel past papers. Easy 71/75 on June 2012 I think it was just the odd format of the practice papers that was putting me off.

Well done, what were the 4 marks you lost? also where do i get these practice papers?
19. Oh my godddd I absolutely hate simplex.

It isn't even hard, it is a pretty easy method but wow it takes such a long time. I spent like half an hour doing a 9 mark question because I was paranoid I had made an error. Then when I came to mark it, I had made an error!
20. (Original post by Knoyle quiah)
Well done, what were the 4 marks you lost? also where do i get these practice papers?
Google "D2 past papers zip" - browse around for 10 minutes and you'll find a zip folder with every D2 past paper/mock paper etc. in existence. Otherwise PM me your email and I'll send you it.

Hung Alg: forgot to increase the value of the numbers crossed twice by the lines.

Misentered something into the table. Poor justification of why a profit equation was optimal. That was it!

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 11, 2013
Today on TSR

### Complete university guide 2019 rankings

Find out the top ten here

### Can I go to freshers even if I'm not at uni?

Poll
Useful resources

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE