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# Another Impossible D1 Paper? [Edexcel] watch

1. (Original post by Toffee_Girl)
Well i completely messed up! I skipped a few questions do the simplex, spend ages tryin to do it then realised how little time i had left so went back but ran out of time to do the dykstra question so im gutted because ive lost simple marks! I literally must have got about 50%. Im gonna revise for monday and fingers crossed my mark from jan plus that will some how drag up my grade!

Did anyone get -1/5 for the pivot at any point in the simplex and what was your maximum flow in the last question?

I think that the theta value has to be positive when considering it for pivot. So the pivot is on the row with the lowest positive theta value.
2. aargh. dropped another mark there then. i used -1/5
3. Yea I got 53 couldn't be bothered to work out the second bit though. I reckon I probably got about 45-50 out of 75 what do u reckon it will be. I think that paper was alot easier than January though, could not answer any q in January and somehow still came out with 45/100 Meah grade boundries will be higher to get an A in this paper
4. This paper i fink was one of the longest and defintiely the hardest D1. I had no time to do last qs and for first 3 chapters they just asked 1 qs!!!! It was definitely harder than D1 jan 05. Hopefully a 45/75 an A?
5. Max flow of 113 anyone?
6. (Original post by Syncman)
Just did D1.
There was a question, draw the activity network. Then part b was explain why you need 2 dummy activities.
Well i drew it, checked it, double checked it and i only needed 1.
Anyone else get that?
You had M and N that were dependant on L, and then two other activities elsewhere. To connect these four activities to an ending node, you had to do a dummy form either M or N to that end node. If you didn't, you ended up with two arcs between two nodes.

At least that's how I interpreted the second dummy (the first was easy to spot).

As for the paper overall, it was lovely! I hope the 100/100 UMS boundary is as low as it usually is.
7. wats the UMS for 100 usually? wat was it for jan this year?
8. (Original post by pumpkinstein)
Oh, that reminds me, did anyone find the maximum flow in the last question? Was it 11 more than the flow already shown? I think I did the working alright, but I managed to make a diagram where the sources put out more than the sinks took in =/

Gah, down with anarchy =(

Martin
I found three flow-augmenting paths. One had a flow of 10, another had a flow of one, and another two (in that order).

It all came out lovely when I used the min cut/max flow theorem, anyway, so I'm almost sure I got it all right.
9. It was 50 /75 for 80 and 44/50 for 70 so probably 62/75 for 100 ums in January
10. (Original post by JohnSPals)
I found three flow-augmenting paths. One had a flow of 10, another had a flow of one, and another two (in that order).

It all came out lovely when I used the min cut/max flow theorem, anyway, so I'm almost sure I got it all right.
One definetly had a flow of 2 that was the only one I managed to do before the time ran out. Could have easily have done that q given 5 more minutes oh well you win some you lose some
11. 50/75 for an A
44/75 for a B
therefore 62/75 for 100/100
However due to the fact that more people take it summer the probability of the actually scales is likely to be in region of 46-50 for an A (80UMS) as it was only 46 in Jun 03 and to be honest that paper was easy from what I've done much more simple then one today.
6 marks per way decided 10 ums from the A boundary (on average for the 2 years)
12. (Original post by Spikerocker)
One definetly had a flow of 2 that was the only one I managed to do before the time ran out. Could have easily have done that q given 5 more minutes oh well you win some you lose some
As far as the flow-augmenting questions went, it wasn't too tough. There were three paths, but none of them were especially hard to spot.

I personally didn't like the Simplex question. It wasn't too tough, but there didn't seem to be anything to it. You started a question, but didn't get the satisfaction of coming up with an overall solution; it was just analysing a tableau that wasn't really consequential to the outcome!
13. (Original post by XYTER)
Max flow of 113 anyone?
i got 109, not confident about it though. was a rushed attempt since i did it last with about 20 minutes left.

i also did get 9100 somewhere, but i just left it in the tableaux, and skipped the rest of the question.

why did my f**king class decide to argue against myself and one or 2 others in our want to do stats!!!! argh, im sure stats wouldve been so much nicer than this.
14. wat was the flow?, i got 100 but im sure its wrong cos ppl wer tellin me they got 109 or 113.
15. You get 109 by doing it the regular way
You get 113 when considering backflows
16. (Original post by matt.forster)
i got 109, not confident about it though. was a rushed attempt since i did it last with about 20 minutes left.

i also did get 9100 somewhere, but i just left it in the tableaux, and skipped the rest of the question.

why did my f**king class decide to argue against myself and one or 2 others in our want to do stats!!!! argh, im sure stats wouldve been so much nicer than this.
Yer too right. Our Teacher said owww you'll get 100 on this there shouldn't be a problem. So me being a stupid individual didn't bother revising for jan 2005 and barely passed. I hate D1. Also Stats probably has more use anyway.
17. (Original post by matt.forster)
i got 109, not confident about it though. was a rushed attempt since i did it last with about 20 minutes left.

i also did get 9100 somewhere, but i just left it in the tableaux, and skipped the rest of the question.

why did my f**king class decide to argue against myself and one or 2 others in our want to do stats!!!! argh, im sure stats wouldve been so much nicer than this.
hehe not to rub it in but the S1 paper this year was the easiest they have ever set
18. I really think that D1 was also the easiest one I have seen...not that I did well in it though...
19. i did get 109 for the flow but i changed it to 117.
i found a min cut which was 117 so i assumed it was 117.

i think i messed the flows question.
20. D1 is only easy if u know what ur doing. Usually there are lots of ppl that dont even turn up to exam and alot of low marks. Hence the lower grade boundaries in june, when ppl have to pay for them like jan resits they usually try harder. I dont think the grade boundries will be any different. I estimate around 50 for A and around 60 for 100UMS.

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