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

1. (Original post by Nitrogen)
Yes its those question! Can you tell me how to tackle them please
Well you have to think logically about where you want to start Usually you want to start and finish from a certain place.... it's kind of hard to explain Questions can be quite unique in that respect and there is no real unified technique for all of those questions... they're not hard though honestly, it would be easier if you could post a question you are having trouble with
2. (Original post by posthumus)
Well you have to think logically about where you want to start Usually you want to start and finish from a certain place.... it's kind of hard to explain Questions can be quite unique in that respect and there is no real unified technique for all of those questions... they're not hard though honestly, it would be easier if you could post a question you are having trouble with
Thank you, I think I understand it by looking through the mark scheme now Good luck with the exam!
3. (Original post by Nitrogen)
Thank you, I think I understand it by looking through the mark scheme now Good luck with the exam!
Great, np... best of luck to you too !
4. (Original post by posthumus)
It really doesn't matter if it's eulerian... the only exception is if they state in the question, for example: your office is at node 'x'
My Teacher keeps marking my Scheduling Questions wrong...

Are there multiple ways of doing Scheduling Questions? I am not quite sure how to "fit in" the tasks which are not critical. It's fairly annoying.

Any help would be great
5. (Original post by Better)
My Teacher keeps marking my Scheduling Questions wrong...

Are there multiple ways of doing Scheduling Questions? I am not quite sure how to "fit in" the tasks which are not critical. It's fairly annoying.

Any help would be great
When you have the critical path, it is the first thing you plot on the first line (first worker). This should just be a continuous 'rectangle' split into each task.

The rest I don't think there is a certain technique or algorithm to put them in order... but I try and go through the tasks in alphabetical order That just seems like how they get it done in the mark scheme.
6. (Original post by posthumus)
When you have the critical path, it is the first thing you plot on the first line (first worker). This should just be a continuous 'rectangle' split into each task.

The rest I don't think there is a certain technique or algorithm to put them in order... but I try and go through the tasks in alphabetical order That just seems like how they get it done in the mark scheme.
Okay thanks I will try in alphabetical order. Thanks so much.

I still have 2010-2012 to finish in the next 3/4 days...argh. So I will hand them all to my teacher and try that method. On an A at the moment but still making small mistakes according to the Markschemes so need to Iron them out FAST haha !

Thanks again
7. (Original post by Better)
Okay thanks I will try in alphabetical order. Thanks so much.

I still have 2010-2012 to finish in the next 3/4 days...argh. So I will hand them all to my teacher and try that method. On an A at the moment but still making small mistakes according to the Markschemes so need to Iron them out FAST haha !

Thanks again
I still need to start I am trying to do as much chemistry as I can this week, then from next week I am doing D1 & M1 only (And it's been nearly a year since I've done any M1 :/ ).

And your welcome best of luck finishing those papers
8. (Original post by posthumus)
I still need to start I am trying to do as much chemistry as I can this week, then from next week I am doing D1 & M1 only (And it's been nearly a year since I've done any M1 :/ ).

And your welcome best of luck finishing those papers
Actually you don't have acess to the JAN* 2013 answer booklet do you?

Found it!! Yay, if anyone needs it I can Inbox them the link!
9. So i haven't started learning it yet, but wondering how easy it is and could i learn it in 7 days?
10. (Original post by Jammy4410)
So i haven't started learning it yet, but wondering how easy it is and could i learn it in 7 days?
Although I have sat it before... I will be starting from next week recapping on all the ideas.

You can get all the ideas/algorithms learnt within 3 days I would say But don't be fooled, get lots and lots of practice before you enter the exam hall I was ignorant to think it would be a walk in the park, and I ended up with the lowest grade obtained yet in my A levels (Boarder line of a D - 50 UMS)

Good luck!
11. (Original post by Better)
My Teacher keeps marking my Scheduling Questions wrong...

Are there multiple ways of doing Scheduling Questions? I am not quite sure how to "fit in" the tasks which are not critical. It's fairly annoying.

Any help would be great
There are 2 sorts of scheduling questions:

1. If you have got to get it done in the critical time, regardless of how many workers it takes, then yes, give a path of critical activities to one worker. It can then be useful to work out the latest start time for each activity, i.e late time at finish - duration, to see which activities are most urgent. You must keep checking on the network as to whether an activity can start yet.

2. Fixed number of workers, the project will have to finish late. In this case, do NOT give the critical activities to one worker. Start using the latest start times for the activities straight away, doing those with the smallest latest start times first.

With either version, don't forget to answer the question, i.e. state either the minimum number of workers or the time.
12. (Original post by tiny hobbit)
There are 2 sorts of scheduling questions:

1. If you have got to get it done in the critical time, regardless of how many workers it takes, then yes, give a path of critical activities to one worker. It can then be useful to work out the latest start time for each activity, i.e late time at finish - duration, to see which activities are most urgent. You must keep checking on the network as to whether an activity can start yet.

2. Fixed number of workers, the project will have to finish late. In this case, do NOT give the critical activities to one worker. Start using the latest start times for the activities straight away, doing those with the smallest latest start times first.

With either version, don't forget to answer the question, i.e. state either the minimum number of workers or the time.
Okay I will probably have to do another Question to get what my head around it. From my understanding 1. Critical Activities, and then fill in the blanks based on the Latest time on the Activity Network for that Activity.

2. I never knew you could get a question like that so I am very glad you said that. I'm assuming these are just Projects where a Critical Path doesn't exist, but Critical Activities exist. So on these types of Questions just fill in the Blanks based on the latest time you can get something done, but prioritizing on the "Biggest" activities or highest duration activities first.

Thanks again so much for trying to clear things up. This one I'm a bit iffy about but again I am about to do 2 Papers now so I will try your method.

+ Everyone was right as well with the Finding a Path in Route Inspection Questions its really really helped me. Going from the Outside to the inside. Thank you guys again. Really appreciate it.
13. Does anyone know how to find the

1. Number of Swaps
2. Maximum Number of Phases

In Bubble sort?

The 2013 Paper had some tricky questions and I want to be prepared if they ask something like this.
14. (Original post by Better)
Does anyone know how to find the

1. Number of Swaps
2. Maximum Number of Phases

In Bubble sort?

The 2013 Paper had some tricky questions and I want to be prepared if they ask something like this.
I don't see a bubble sort question on the 2013 paper? Are you on Edexcel?
They only really tend to ask the maximum number of iterations or swaps after you have applied the algorithm, so if your algorithm is applied correctly - then you've basically worked out the answer already.
15. (Original post by Westeros)
I don't see a bubble sort question on the 2013 paper? Are you on Edexcel?
They only really tend to ask the maximum number of iterations or swaps after you have applied the algorithm, so if your algorithm is applied correctly - then you've basically worked out the answer already.
Yes I'm on Edexcel.

I'm asking because in the Exam Style Questions we were given in Class, they asked how do you work out the No of Swaps that have happened.

And apparently if its like a Set of 7 Elements you do
6x5x4x3x2 or something like that but I'm not sue.
16. (Original post by Better)
Yes I'm on Edexcel.

I'm asking because in the Exam Style Questions we were given in Class, they asked how do you work out the No of Swaps that have happened.

And apparently if its like a Set of 7 Elements you do
6x5x4x3x2 or something like that but I'm not sue.
I remember my teacher mentioning something about that but it was confusing so I can't remember lol...
Ill ask again on Tuesday

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17. (Original post by Better)
Yes I'm on Edexcel.

I'm asking because in the Exam Style Questions we were given in Class, they asked how do you work out the No of Swaps that have happened.

And apparently if its like a Set of 7 Elements you do
6x5x4x3x2 or something like that but I'm not sue.
I just looked into it, apparently:

For a list of n elements, the max. number of interchanges is
(1/2)n^2 - (1/2)n

So for a list of 6 elements
(1/2)6^2 - (1/2)6
(1/2)36 - 3
18 - 3 = 15 interchanges
18. (Original post by Westeros)
I just looked into it, apparently:

For a list of n elements, the max. number of interchanges is
(1/2)n^2 - (1/2)n

So for a list of 6 elements
(1/2)6^2 - (1/2)6
(1/2)36 - 3
18 - 3 = 15 interchanges
That is pretty complex......Is there anything more simple anyone?

Argh I was supposed to finish all the 2011 Papers today...so annoying I want to have all the Papers finished by Monday ! Damn Physics!
19. (Original post by Better)
That is pretty complex......Is there anything more simple anyone?

Argh I was supposed to finish all the 2011 Papers today...so annoying I want to have all the Papers finished by Monday ! Damn Physics!
I've never even seen a question where they ask you for that! Unless it's after you've applied the algorithm! Find me one?
20. (Original post by Westeros)
I've never even seen a question where they ask you for that! Unless it's after you've applied the algorithm! Find me one?
It might have been in the End of Chapter Sheets for MEI but I dunno if you haven't seen anything like that then don't worry...

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