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# AQA Decision 1 23rd January 2012

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1. Re: AQA Decision 1 23rd January 2012
(Original post by Dangerous Theory)
Every vertex does not need to be boxed before reaching the final vertex. Only one past paper has had a question like this and one of the vertex values remained unboxed. The comment in the mark scheme was "condone boxed at X", so it didn't lose you marks for doing it but it technically shouldn't be done. I shouldn't worry, it's unlikely to appear IMO.

I would define a tour as a trail that starts and finishes at the same vertex of graph, visiting every other vertex in between, eg ABCDA. Each vertex should only be visited once, and the start/finish vertex should only be visited at those points.

It's not concise, I know, but I think that pretty much covers it.
thanks very much so for a tour, can you only use an edge once as well?
2. Re: AQA Decision 1 23rd January 2012
(Original post by timoaf)
thanks very much so for a tour, can you oYnly use an edge once as well?
Yes, because reusing an edge would be revisiting a vertex. Only start vertex is revisited at the end, but that's always via a different edge.
3. Re: AQA Decision 1 23rd January 2012
Oh I nearly had a fit, saw 23rd in the title and thought I had missed my exam today! Hahhaa. Silly me.

No idea how I got a D first time round, hoping to pull out a B/A need a B overall in maths for uni!
4. Re: AQA Decision 1 23rd January 2012
(Original post by Lizzie.)
Oh I nearly had a fit, saw 23rd in the title and thought I had missed my exam today! Hahhaa. Silly me.

No idea how I got a D first time round, hoping to pull out a B/A need a B overall in maths for uni!
Ditto with the D. I have no idea how I got 58 UMS in January, considering I've been doing the past papers in 50-60 mins and getting around 70 marks (always losing some because I'm too lazy to check for mistakes in practice tests).

Good luck tomorrow!
5. Re: AQA Decision 1 23rd January 2012
Well that went terribly...

that linear programming completely threw me, as did the last part of Dijkstra and I think I got the lower bound wrong. I always get the lower bound wrong -_-

It flopped.
6. Re: AQA Decision 1 23rd January 2012
(Original post by antonyzac)
Well that went terribly...

that linear programming completely threw me, as did the last part of Dijkstra and I think I got the lower bound wrong. I always get the lower bound wrong -_-

It flopped.
I found it a hard paper too

The Linear programming equations I just freaked out LOL the 40% one I could not get at all

I managed to get a good feasible region though.

Also I found Question 4 (I think) on the graphs just went over my head. Which is Hamiltonian etc.
7. Re: AQA Decision 1 23rd January 2012
(Original post by Mr XcX)
I found it a hard paper too

The Linear programming equations I just freaked out LOL the 40% one I could not get at all

I managed to get a good feasible region though.

Also I found Question 4 (I think) on the graphs just went over my head. Which is Hamiltonian etc.
I thought the graph theory was fine. Hamiltonian is just something which visits all vertices once apart from the start. 3 edges gave you a Eularian trail and Hamiltonian cycle if that's what you mean.
8. Re: AQA Decision 1 23rd January 2012
(Original post by antonyzac)
I thought the graph theory was fine. Hamiltonian is just something which visits all vertices once apart from the start. 3 edges gave you a Eularian trail and Hamiltonian cycle if that's what you mean.
Yeye, I found it really hard LOL :/

I got which is which etc but I think my answers where not right.

Probably got 2 marks out of 8 for that question
9. Re: AQA Decision 1 23rd January 2012
(Original post by Mr XcX)
Yeye, I found it really hard LOL :/

I got which is which etc but I think my answers where not right.

Probably got 2 marks out of 8 for that question
What do you think you got overall? I think I got 54 minimum, because that linear programming killed me. I saw it talking only about soft and medium and not firm and was like WTF! And then it completely knocked me down.
*moooaaannn*.
10. Re: AQA Decision 1 23rd January 2012
(Original post by antonyzac)
What do you think you got overall? I think I got 54 minimum, because that linear programming killed me. I saw it talking only about soft and medium and not firm and was like WTF! And then it completely knocked me down.
*moooaaannn*.
Around about same.

54 - 64 which is around B and A mark. I resit this exam cause I last time in Jan got B but I think I have just got a B again LOL.
11. Re: AQA Decision 1 23rd January 2012
(Original post by Mr XcX)
Around about same.

54 - 64 which is around B and A mark. I resit this exam cause I last time in Jan got B but I think I have just got a B again LOL.
It's my first time but it looks like I'll be resiting maybe be resiting C3, D1 and probably C4 next year x)
Love my life (y).
12. Re: AQA Decision 1 23rd January 2012
(Original post by Mr XcX)
I found it a hard paper too

The Linear programming equations I just freaked out LOL the 40% one I could not get at all

I managed to get a good feasible region though.
This took my a while, but I got it in the end:

(I can't do 'greater than or equal to' sign, so just assume that all '>/<' are or equal to, from now on.)
I believe it was y > 40/100(x+y+z)

*2x=z, therefore z=0.5, x=1+z.*

y>40/100(1.5x+y)
y>3/5x + 2/5y. *-2/5y from both sides*
3/5y>3/5x *multiply by 5 on both sides*
y>x

Don't stress though, because that was tricky and probably 1, max 2 marks out of 3.

I'm assuming you could do the other two equations?
13. Re: AQA Decision 1 23rd January 2012
I found the exam ok, but it could have gone a lot better
The last 3 marks of question 9 completely threw me, I got 1100 pillows and for the last question 200 soft, 400 medium and 100 firm but that was too expensive :L what were you supposed to do? I've only ever done linear programming with an objective line/equation
Also, what did everyone get for the commenting on the lower bound diagram question??? I just put that it was a tour :L
14. Re: AQA Decision 1 23rd January 2012
will some1 please make unofficial mark scheme
15. Re: AQA Decision 1 23rd January 2012
Basically, you have
x=2z so z=0.5x

You can now plot an objective line with this information. He wants to maximise the total pillows bought (x+y+z), and because z=0.5x, you get:
N = 1.5x+y

and that is your objective line. Solve normally thereafter
16. Re: AQA Decision 1 23rd January 2012
(Original post by Harantony)
Basically, you have
x=2z so z=0.5x

You can now plot an objective line with this information. He wants to maximise the total pillows bought (x+y+z), and because z=0.5x, you get:
N = 1.5x+y

and that is your objective line. Solve normally thereafter
That's not true. It didn't require an objective line due to the nature of the problem. You simply had to find the point inside the FR where x+y was greatest (the point 100,400) then use the information that x is twice z to deduce that you must include 50z also --> 100x, 400y, 50z pillows (550max)
17. (Original post by Dangerous Theory)
That's not true. It didn't require an objective line due to the nature of the problem. You simply had to find the point inside the FR where x+y was greatest (the point 100,400) then use the information that x is twice z to deduce that you must include 50z also --> 100x, 400y, 50z pillows (550max)
I think it helped though if you drew the objective line You don't have to but as long as you got the right answer (which I didn't) you're fine

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18. Re: AQA Decision 1 23rd January 2012
(Original post by Dangerous Theory)
That's not true. It didn't require an objective line due to the nature of the problem. You simply had to find the point inside the FR where x+y was greatest (the point 100,400) then use the information that x is twice z to deduce that you must include 50z also --> 100x, 400y, 50z pillows (550max)
In past papers the examiners' report had said that an objective line would be useful to draw. Either way it gave me the same answer
19. Re: AQA Decision 1 23rd January 2012
(Original post by Harantony)
In past papers the examiners' report had said that an objective line would be useful to draw. Either way it gave me the same answer
Okay, fair enough, I suppose that does work. Just as long as you didn't say that X is 1.5 times the co ord of X (which is how I initially interpreted your post).
20. Re: AQA Decision 1 23rd January 2012
I failed this exam, we'll all agree that I could have done so much better than 99/100

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