Edexcel Maths D1

Gamaya

No, that's what objective functions are written as. Check past mark schemes, too.

Do you think i would get penalised if i wrote it the other way?

Reply 41

not to try and make you worry, but yes! that's not how objective functions are written. =/ :frown:

Reply 42

Ancient18

I thought that paper was harder than any past paper id done before on D1.
The paper went quite Ok until i got to Simplex where i just couldnt believe the answer i did get 150 though. The problem was i spent so much time redoing simplex that i didnt check the paper again and only 5 minutes before end of time i realised i had made a fatal mistake on the prims where i had overlooked one value and therefore my tree was wrong. I didnt manage to redo it because i panicked and messed it up again ah well i hope i get the method marks at least :-(. Im really annoyed because i always got 95% on past papers and mocks :-(

I also didnt manage to identify the purpose of the alogorithm but thats only 2 marks :smile:

All in all i reckon the worst i got on the paper was a medium B also since most people said it was hard i am hoping the boundries will go down.

BTW: did you know simplex is going to be removed from the D1 syllabus and included in D2. We are apparently the last year having to do simplex in D1 *grml*

Reply 43

Gamaya

not to try and make you worry, but yes! that's not how objective functions are written. =/ :frown:

Oh well, doesn't matter, it was only 1 mark anyways (i think). What do you lot think the grade boundaries are going to be this year???

50/75 for an A? And 60/75 for 100UMS?

Reply 44

Couldnt' say, but in the past it's been around 55/75 for an A.

Reply 45

melissabee

7

Gamaya

Rainbow24, I got 3402, it was the two original x and y's multiplied together. And I thought the paper went really well. For the route inspection I got 39 and so did all my other friends who do further maths, too. Managed to get 19 on the flow network (you had to use backflow twice) and for the simplex, the profit was 150 (you only needed two tableaux but the arithmetic got messy with sixths and ninths).

What did people get for the Prim one? I got 860 as the minimum weight of the spanning tree but two of my classmates got 864. If I've made a mistake fair enough but 860 is less than 864 and therefore surely had to be the right answer.

All in all though I think I've only dropped a few marks and I'm happy about the paper :smile:

The simplex was horrible, especially since I realised that I got one of the initial values wrong (the one that involved alot of 1/6s and 1/9s) and had to retrace my steps about 5 mins before the exam ended.
Otherwise I thought it went quite well, atleast better than what I got in january.

Reply 46

I found it really hard just to remember to do the correct row operations (like, after I'd decided upon them and having to work out each new value) and the correct numbers to use (because you have to look at both the new number and the one from above/below in the previous tableau)! But I managed to get there which was a mighty relief.

Reply 47

Gamaya

I found it really hard just to remember to do the correct row operations (like, after I'd decided upon them and having to work out each new value) and the correct numbers to use (because you have to look at both the new number and the one from above/below in the previous tableau)! But I managed to get there which was a mighty relief.

Same here, i'm just so happy i used a pencil for the simplex question.

Reply 48

melissabee

7

John.

Same here, i'm just so happy i used a pencil for the simplex question.

I wish I'd done that!

Reply 49

There wasnt enough time!!! I didnt have any time to spare, down to the last second i was scribbling in a back flow which id just found meaning i could send 19 through the flow! I didnt even know that what i was doing was back flow, i just saw a path i could send 4 already going through, meaning i could send more through :p:

But hey i did that anyways xD
That simplex was evil! I kept getting random fractions, im sure one of them i got was 11 and 2/3, even if its wrong i should get a few marks for method.
The one thing i hated most about the paper was the algorithm!! I think i got around 3042? But either way i found it quite hard, and had no idea what it proved :s:

Reply 50

~NC~

There wasnt enough time!!! I didnt have any time to spare, down to the last second i was scribbling in a back flow which id just found meaning i could send 19 through the flow! I didnt even know that what i was doing was back flow, i just saw a path i could send 4 already going through, meaning i could send more through :p:

But hey i did that anyways xD
That simplex was evil! I kept getting random fractions, im sure one of them i got was 11 and 2/3, even if its wrong i should get a few marks for method.
The one thing i hated most about the paper was the algorithm!! I think i got around 3042? But either way i found it quite hard, and had no idea what it proved :s:

I think you mean 3402 for the algorithm, which was the correct answer. As it was simply just finding the multiplication of 54 x 63 = 3402.

Reply 51

nice_to_be_back

When doing algorithms if 'INT' appears in a flow diagram what does this mean?

Reply 52

John.

I think you mean 3402 for the algorithm, which was the correct answer. As it was simply just finding the multiplication of 54 x 63 = 3402.

Yer that sounds ok :p:

I think i got around that ;yes; So was that what the algoruthm was finding, multiplication? I put multiples of 9 :p:

Im just so glad i never have to do D1 again!! role on c4, mmm pure maths :biggrin:

I must say i was so glad when define planar graph came up as the first question, cos my friend asked me what it was about ten mins before, so i checked it, meaning we both knew it off by heart woo!
And for the gantt chart did you all get 4 workers as minimum, but 5 needed?

Reply 53

nice_to_be_back

When doing algorithms if 'INT' appears in a flow diagram what does this mean?

Ive got no idea :s:

Reply 54

gooner88

10

So what did everyone do for flow augment questiont? Also, they already did the minimum cut for us so how could we prove max flow was maximal otherwise.

For increasing the flow question, I increased it by 4,10,1,2 and 2 which adds up to 19. Anyone get any similar.

Reply 55

gooner88

So what did everyone do for flow augment questiont? Also, they already did the minimum cut for us so how could we prove max flow was maximal otherwise.

For increasing the flow question, I increased it by 4,10,1,2 and 2 which adds up to 19. Anyone get any similar.

Yer i got the same!!! And did you get the 2's through backflow? If so yay :biggrin:

And lol i know what you mean about the min cut-max flow, i just said min cut is 104, therefore max flow is 104 :p:

Reply 56