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# Decision Maths 1 - Wed 16th June watch

1. (Original post by Babygal)
lucky thats not on my syllabus i'm doing ocr mei. and glad i've never heard of that
Do you know if the Travelling Salesperson algorithm thing is on the OCR MEI syllabus? It's in the textbook, which by the way one of the worst textbooks I've ever come across in my life, but I've not done it in class.

I did D1 in January but I'm re-sitting it. I found the paper really difficult compared to past papers and ran out of time. The last question was about Linear programming was worth something like 15 marks IIRC and I don't think I got a single one. Still managed to get a C somehow (although at 60/100 it was the bare minimum I could have got away with...).

Lucky I'm re-sitting it though, becuase I know I did absolutley awful in S1 which is really embarassing as its probably the easiest of the three module I'm doing this year
2. (Original post by Jubba)
some1 please explain the max flow min cut theorom! how do u recognise cut? i never see it!
Do you cut through all the SATURATED paths (i.e. the paths that have used up all their capacity and have no spare capacity.)? Add up the numbers on the arrows heading towards the sink node and if this equals the flow, then the flow is maximal.
3. There is no set way of finding the minimum cut as far as i know. You just find it by inspection. However you do know what value you are looking for (as the minimum cut is equal to the maximum flow, which you should have found) so you just keep looking until you find a value that is equal to your maximum flow. It is q. difficult sometimes to see it sometimes, but you will find it eventually if you keep looking. If not, dont worry it's only worth a mark or two.
4. You can cut through any, not just saturated, paths. You add up their capacities to form a cut value. The only condition is that the cut must completely block any flow from source to sink.
5. ive got edexcel decision and discrete on monday, so wot sort of stuff shall i revise coz ma teacher aint been in much, an i need to learn sum of d syallabus, ne 1 no of ne past paperz??
6. I have D1 too, in under 13 hours (EdExcel). I'm glad everyone else hates it sooo much, I hate it too...it nearly made me cry earlier cuz I don't understand flows or matchings! Still don't, damn things. With high marks on other maths modules, I can afford a low(ish!) mark on D1, but I am worried I won't get the ABB required for University of York! Unlike some of you, I cannot retake D1 (well I can but I miss a year of uni!)...this is my 1 and only go at it...I got an E in the mock without revising so I shouldn't fail! He hopes!
Simplex Tableaux are OK....I've followed it through and it's fine...I don't *understand* what I'm going I just learn the steps, but as for all these algorithms, blow me down! Odd vertices here, even vertices there, Eulerian graphs over there and a Hamiltonian cycle graph here too- and, oh, prove that this is Planar boring (pun intended)

Not maths I agree, but I hope an A is in order.

I remember for Planar algorithm it's
1) Find Hamiltonian cycle
2) Redraw Hamiltonian cycleas a regular polygon
3) Then do all your bits and bobs like elastic stretching it outside, and if none cross it's planar.

For the other algorithms, having to remember that you have to start at an odd vertex and end at an odd vertex, it's doing my head in!

Ahhh
"Countdown" Kirk
7. can some one expalin to me scheduling and Gantt Charts.... or a suitable website... thanks
8. Yeah, I couldn't do Cascade (Gantt) Charts either, and guess what, they came up!!! I revised simplex tableuax like mad, and thought "yes, I can do this now, 16 marks in the bag for me!" and to my horror, on the exam today, simplex tableaux did not appear!!! Grrr, linear programming did though, but I messed up my axes, and so I couldn't fit all my lines on my graph in, and I ran out of time! Damn decision. Hope I made a B grade though.

As for tomorrow (well today I should say) I have an exam in 8 hours. That being AQA Business Studies Unit 4, followed by AQA Business Studies Unit 5, followed by quarantine for EdExcel Physics Unit 4, followed by EdExcel Physics Unit 5 (these physics exams should be taken in the morning) - followed by OCR General Studies Unit 6. A fair old bag today! 5 exams, spanning from 9am till 5:30pm. Oh deary me...I'm dreading this!

Kirk
9. (Original post by Pegasus)
Do you know if the Travelling Salesperson algorithm thing is on the OCR MEI syllabus? It's in the textbook, which by the way one of the worst textbooks I've ever come across in my life, but I've not done it in class.

I did D1 in January but I'm re-sitting it. I found the paper really difficult compared to past papers and ran out of time. The last question was about Linear programming was worth something like 15 marks IIRC and I don't think I got a single one. Still managed to get a C somehow (although at 60/100 it was the bare minimum I could have got away with...).

Lucky I'm re-sitting it though, becuase I know I did absolutley awful in S1 which is really embarassing as its probably the easiest of the three module I'm doing this year

I have D1 on Monday i know 3 parts out of probably 6, no chance of me passing, my stats went bad and pure was ok, but thats not going through (long story) so me failing math this year 95%

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