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# D1 (Decision 1) 17 May 2013 Official Thread watch

1. (Original post by Epic Flawless)
Of course, they are!

I'm worried about making a mistake in the exam, because I know that would be deadly in decision since the following questions always stem from the first (e.g inspection, CPA, Dijkstra's). Especially because I was making silly mistakes in the mechanics exam, but fortunately, I had enough time to check, idenify and correct them.
You know the way I do it, is I start the questions from the end and work my way forward, not from 1st question to last, because I dont know about you but with D1 your brain gets tired more quickly as you are using a lot of energy to check your work and to deal with patterns and cycles. I think linear and critical requires a lot from your brain.

Okay more defintions

define: distance matrix
define: connected graph
define: minimum spanning tree
2. (Original post by otrivine)
You know the way I do it, is I start the questions from the end and work my way forward, not from 1st question to last, because I dont know about you but with D1 your brain gets tired more quickly as you are using a lot of energy to check your work and to deal with patterns and cycles. I think linear and critical requires a lot from your brain.

Okay more defintions

define: distance matrix
define: connected graph
define: minimum spanning tree
Hmm, maybe that is a good idea but I want to do all the easy stuff so I feel confident for the more tricky critical path analysis and Linear programming

A distance matrix is a matrix showing the weight on the arcs between vertices.
A connected graph is a graph in which there is a path between every vertex.
A minimum spanning tree is a tree that contains all of the vertices of the graph, such that the total weight on all of the arcs is a small as possible

Ok, I'm going to bed. Good night. :/
3. (Original post by Epic Flawless)
Hmm, maybe that is a good idea but I want to do all the easy stuff so I feel confident for the more tricky critical path analysis and Linear programming

A distance matrix is a matrix showing the weight on the arcs between vertices.
A connected graph is a graph in which there is a path between every vertex.
A minimum spanning tree is a tree that contains all of the vertices of the graph, such that the total weight on all of the arcs is a small as possible

Ok, I'm going to bed. Good night. :/
nicely said, sure

Good night!
4. can anyone explain scheduling to me? I just can't get my head around it...

thanks
5. (Original post by Strawberry x3)
can anyone explain scheduling to me? I just can't get my head around it...

thanks
If you go on google and type maths247 , on his website he posted video on scheduling.

Hope this helps
6. (Original post by Strawberry x3)
can anyone explain scheduling to me? I just can't get my head around it...

thanks
You have to build a schedule, usually from a gantt chart like get all your little blocks together. The idea is, from the scheduling diagram you can see how many workers you would need to complete all the tasks (number of rows = number of workers needed). The first row is usually a continuous row which consists of the critical activities.
The rest you slot in like a jigsaw, and see how many rows you get...

... hope you kind of got that though it would be easier to explain, if you could post a question/ example here
7. (Original post by Dilzo999)
So any revision tips? I just keep making the most silliest mistakes anyone know how to conquer that? e.g. mistakes in bubble sort like missing a number or not having the final pass or something like that.
Take your time and double check before you go onto the next iteration/pass!
8. I wanted to confirm, sometimes in linear programming we are asked to write down the objective function (max), if they say 60p is the number of x and 50p is the number of y

we do Pmax = 0.50x + 0.60y

thats how I do it, but sometimes in mark schemes they do Pmax= 50x + 60y without putting the 0 point, do both functions lead to the correct solution when finding the profit?
9. Can someone help me on Mixed Exercise 1F, Question 2b.

It's a bubble sort question and asks for the maximum number of interchanges needed to sort a list of six pieces of data? How do I work this out? Also what does the term interchanges actually mean?

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10. (Original post by Westeros)
Can someone help me on Mixed Exercise 1F, Question 2b.

It's a bubble sort question and asks for the maximum number of interchanges needed to sort a list of six pieces of data? How do I work this out? Also what does the term interchanges actually mean?

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How many passes did you get for part a)
11. (Original post by Westeros)
Can someone help me on Mixed Exercise 1F, Question 2b.

It's a bubble sort question and asks for the maximum number of interchanges needed to sort a list of six pieces of data? How do I work this out? Also what does the term interchanges actually mean?

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Can someone check if I am doing the right method,

because there are 4 passes, and in question it states 2 values are interchanged, we do 4 x 2 =8 and because there are 6 numbers we then add
12. (Original post by Westeros)
Take your time and double check before you go onto the next iteration/pass!
I got the answer for your question on the interchange you just do

5+4+3+2+1= 15
13. Anyone think I can complete all past papers within today and tomorrow? I've been putting it off as It's easy and I have Economics on the same day XD. Only thing I find troubling is Linear programming.
14. I did May 2009 paper and just wanted to ask a question..for question 3, Bipartitate graph..the c part..starting from E, does it have to go all the way to 6 like they did in the mark scheme or can I do

E-5=r-4 then cs

then from h-1=s-3=c-6
then you get the same answer...?

http://www.mathsgeeks.co.uk/pdf/C2Ed...elJune09MS.pdf
15. have you guys done the solomon, some questions are so challenging and weird?
16. My teacher told me most of the questions are do-able but some of the questions in Solomon are from the old specification so not to do ones which look weird/contain things you don't know about.
17. (Original post by otrivine)
have you guys done the solomon, some questions are so challenging and weird?
Solomon Papers are the old specification, so you should ignore questions about simplex networks, the ones with the dotted lines, and planar graphs :-)

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18. (Original post by Westeros)
Solomon Papers are the old specification, so you should ignore questions about simplex networks, the ones with the dotted lines, and planar graphs :-)

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But for example this question on Linear programming is quite challenging

question 6a)ii
do you know how to do it?
19. (Original post by otrivine)
But for example this question on Linear programming is quite challenging

question 6a)ii
do you know how to do it?
I'm going to make that my first past paper of the day So I'll let you know how I personally find it !

I just hope those long algorithm flow chart thingies don't come up this time round :s I don't think they will though... because it came up in January ? Was so long winded, that I didn't even attempt it.
20. (Original post by posthumus)
I'm going to make that my first past paper of the day So I'll let you know how I personally find it !

I just hope those long algorithm flow chart thingies don't come up this time round :s I don't think they will though... because it came up in January ? Was so long winded, that I didn't even attempt it.
you mean the solomon, the questions the way they are structured is quite different in our text book questions and edexcel papers/

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