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# Arsey's D1 Edexcel Summer 2013 Model Solutions BOTH PAPERS watch

1. Yup I said it had a float of greater than 2 so it could be delayed. I didn't write anything for critical activity.
2. (Original post by lebron_23)
Yeah I did exactly the same, my lines were fine but I indicated R wrong. I've just been looking through old mark schemes and they say 1 mark for each correctly drawn line and then 1 mark for the feasible region indicated correctly and clearly. So I reckon (hope) we'll lose 1 mark on that. Not too sure about the optimal solution question. Looking at old mark schemes, it says 1 mark for any point tested/found using objective line in their feasible region (meaning we get a method mark?) but I'm not sure about the second mark which just says testing another point correctly. Not sure if that means that it has to be in the feasible region or if it can be a point in your own region.

Just hope I got enough ums above a D so it can average out to an A for core maths.. Although I'm almost certain I've got a U.

Meh, life sucks
hopefully i will not lose too many marks for it, can only wait now
3. (Original post by Arsey)
Fairly reasonable paper I thought

1. Matchings - pretty simple, although not breaking down the 2 required paths into separate part of the question, could cause problems.

2. Quick sort and Bin packing - very easy, I thought it was odd how the first-fit decreasing didn't reduce the number of bins though

3. Prim's and Kruskal's - very easy

4. Dikky - harder than normal due to the sneaky part of the route. Quite easy to mank up b) too.

5. Postie - standard. A common error on c) will be to repeat DE.

6. LP - not easy but it never is. Part b) will be a bloodbath.

alt to part b)

no more than 1.5 times as many small as large

for every 3 small you need at least 2 big

7. CPA - Fairly standard but the backward scans not using the dummy paths will be a very common error. Gantt chart took too long. f) and g) will be poorly answered.

Overall I would say it was a little easier than Jan, I would expect it to be around 63 for an A.

This summer I will upload solutions to the following Edexcel papers:

Core 1;
Core 2;
Core 3;
Core 4;
FP1;
M1;
M2;
S1;
D1;
D2.

I will try to get hold of some solutions for FP2; FP3 and M3.

I don't do S2

All papers will be uploaded in line with site rules (please don't PM me asking when I will I be uploading them).
This is probably going to make a few of you laugh, but I did the quicksort in ascending instead of descending, and then did bin packing using the 'first fit ascending bin packing method' which I think i've made up. And said at the end of the question that first fit was better because there were less bins, so it wasn't an optimal solution. Any marks? It's annoying because I got the same as arsey for everything else.
4. I think it's really harsh for Edexcel not to include the letter O on the last question.

For 1b: Will I lose marks for not drawing the complete matchings on the diagram?
For 6d: I wrote x=36, y=39 for some reason and obviously my Cost is wrong as well. Is there any chance I will get any marks for it for example if I drew an objective line and method marks as well?

Overall I think I got about 65/75 for this.
5. For question 7, if you didnt get part a) right, would you not get follow up marks for the rest of it? so the floats and lower bound according to your gantt chart (i also got 5)
6. For 6d I accidentally found the maximum instead of the minimum for the optimal point using the ruler method. How many marks out of 4 do you think i would get??
7. For the quick sort in Q2 I didn't put a circle around the pivots I just used rectangles for the pivots, how much marks would I lose.

And for Q1 the matchings, I worked out the improved matching, but I only used one of the bipartite graphs they gave us ( to draw the new complete matching) I didn't use the second bipartite graph they gave us, so how much marks would I lose?
8. (Original post by LiliMiki)
For 6d I accidentally found the maximum instead of the minimum for the optimal point using the ruler method. How many marks out of 4 do you think i would get??
how did you find the maximum is it's an infinite region?
9. (Original post by Vorsah)
For the quick sort in Q2 I didn't put a circle around the pivots I just used rectangles for the pivots, how much marks would I lose.

And for Q1 the matchings, I worked out the improved matching, but I only used one of the bipartite graphs they gave us ( to draw the new complete matching) I didn't use the second bipartite graph they gave us, so how much marks would I lose?
I doubt you would lose any?
10. (Original post by FLLF)
how did you find the maximum is it's an infinite region?
The question asked for the minimum.
11. (Original post by milworthy)
The question asked for the minimum.
I know, but they said they found the maximum?
12. In the linear programming question the last I work out how he should buy of x and y, but forgot to state the overall cost, how much marks would I lose out of 4?
13. (Original post by FLLF)
I know, but they said they found the maximum?
Instead of using the first point the ruler touched, I used the second. That's what I meant.
14. For the Gannt chart does it matter if you have gaps between an activity and an activity directly below it ?
15. Is there any leeway for the total profit or the x/y values on the LP question? I got the total profit to be 16000 instead of the 16200 present in Arsey's unofficial mark scheme, and I suspect one of my x or y values was one less than it ought to have been due to my abysmal spacial awareness skills.
16. (Original post by LiliMiki)
Instead of using the first point the ruler touched, I used the second. That's what I meant.
ah, then probably 2 if you drew the line right?
17. I was hoping to limit my losses on this module, apart from some ambiguous wording, I think I did really well thanks for the answers
18. (Original post by Vorsah)
In the linear programming question the last I work out how he should buy of x and y, but forgot to state the overall cost, how much marks would I lose out of 4?
From doing past papers I'd say if all your working is there, objective line/ point testing etc, you'll only lose 1 mark
19. Evil Edexcel trying to trick us be removing O lol.
20. Hi, i found the paper ok, but there were 2 things that i'm slightly confused on. The first being i for the route inspection i got 77 twice so i said that you could use both routes as they give the same value; and also for the gantt chart i wrote you would now need 5 workers but 4 would be beneficial to the company due to lower wages does that seem right? thanks!

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