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

1. (Original post by Better)
Correct, no matter what.

By Definition each Activity must be shown Uniquely hence you cannot have a "loop" of Two Activities leaving the same Event (Node) and Ending at the same Event (Node).
Ah okay, thank you for confirming that

Makes sense I guess since you might as well just have them both as one activity if you were going to portray it as a sort of "loop"
2. (Original post by posthumus)
Ah okay, thank you for confirming that

Makes sense I guess since you might as well just have them both as one activity if you were going to portray it as a sort of "loop"
Oh yeah ! I didn't even think of that good point!!
3. (Original post by posthumus)
Ah okay, thank you for confirming that

Makes sense I guess since you might as well just have them both as one activity if you were going to portray it as a sort of "loop"
Hi my friend how are you

can you help me on question

http://www.edexcel.com/migrationdocu...e_20100115.pdf

7)d)

thanks
4. (Original post by otrivine)
Hi my friend how are you

can you help me on question

http://www.edexcel.com/migrationdocu...e_20100115.pdf

7)d)

thanks
Hey It would have helped if you gave me the question paper instead of the answer booklet !

well anyway You can make the x coefficient 1 and since y is 40% greater than x... you can make the coefficient of y 1.4
so you get:

x + 1.4y

to get to the nearest integer Multiply by 5

5x + 7y
5. (Original post by posthumus)
Hey It would have helped if you gave me the question paper instead of the answer booklet !

well anyway You can make the x coefficient 1 and since y is 40% greater than x... you can make the coefficient of y 1.4
so you get:

x + 1.4y

to get to the nearest integer Multiply by 5

5x + 7y
sorry, thanks , hey want to revise definitions?

define:alternating path (2)
6. (Original post by otrivine)
sorry, thanks , hey want to revise definitions?

define:alternating path (2)
It's easy to test yourself, just put them all in a word Document then just go through and see if you know them..... Lets leave this thread just for Questions instead as we have 2 Proper Teachers here who have been helping. Go to Arseys thread which I posted at the front if you are unsure about the definitions too - hope that helps.
7. (Original post by Better)
It's easy to test yourself, just put them all in a word Document then just go through and see if you know them..... Lets leave this thread just for Questions instead as we have 2 Proper Teachers here who have been helping. Go to Arseys thread which I posted at the front if you are unsure about the definitions too - hope that helps.
I agree with you

But I thought maybe testing each other in definition will help us remember, because the definitions are quite difficult in d1 to memorise.
8. So yh I've been going through the D1 Edexcel book and sometimes they ask you to explain something...

... I have no idea and usually just turns back to look at the answers to be like WTF This is the most complex explanation I've seen in my life! (well assuming they are only work 1/2 marks anyway).

Also can someone quickly confirm for me, in critical path analysis... if I have to number the nodes or not ?

9. I'm alright with everything except of linear programming, they always have some next random equations that's the hard part. However objective line method and all the other things are easy.3
10. (Original post by posthumus)
So yh I've been going through the D1 Edexcel book and sometimes they ask you to explain something...

... I have no idea and usually just turns back to look at the answers to be like WTF This is the most complex explanation I've seen in my life! (well assuming they are only work 1/2 marks anyway).

Also can someone quickly confirm for me, in critical path analysis... if I have to number the nodes or not ?

IRight now the only thing that has me confused is Dijkstra's - what did you do to check (usually 2 Marks). I say that I scanned back but I'm not sure if that's enough. I hope my Teacher gets back my 2010-2012 Papers soon!!! Argh I need them back by Friday, he's marked 2005-2009 Papers though.... And sorry to answer you yes when you do the Diagrams you MUST include the number on the nodes. I lost a few Marks in my Early papers not doing this. If you are doing Scheduling you will see the Nodes make things very easy to see Precendence. You can actually work through in Order of Numbering of Nodes, then use the other methods, which Maths24/7 Layed out in his video (making sure you schedule, activities which have the earliest Late Event Time first).
11. It's great everyone is talking about their weakest topics actually - It's making me remember the mistakes I've made!! I won't make those again!!!!
12. (Original post by Better)
IRight now the only thing that has me confused is Dijkstra's - what did you do to check (usually 2 Marks). I say that I scanned back but I'm not sure if that's enough. I hope my Teacher gets back my 2010-2012 Papers soon!!! Argh I need them back by Friday, he's marked 2005-2009 Papers though.... And sorry to answer you yes when you do the Diagrams you MUST include the number on the nodes. I lost a few Marks in my Early papers not doing this. If you are doing Scheduling you will see the Nodes make things very easy to see Precendence. You can actually work through in Order of Numbering of Nodes, then use the other methods, which Maths24/7 Layed out in his video (making sure you schedule, activities which have the earliest Late Event Time first).
Still need to Dijkstra I understand its difficult to find the erm shortest route ? Similar to the early and late time graphs. I just take my time And go over it once more, carefully... however that's time consuming!

Ah darn it, do the numbers have to be in a specific order to get my marks? I don't see the need for numbers.

Also do you think its necessary to use a ruler for gant/scheduling diagrams? Seems like a stupid question But it was too god damn time consuming I did half of it free-hand.... ran out of time and couldn't do some of the first 3 questions I skipped
13. Got my Papers back only got 73/75 on 1 paper, one of the 2012 Papers.

The other papers were low A grades. Which is v v annoying. Going to re-do
- Jan2006-2008, 2011
- The 4 Mock papers, then the 2012 Papers.

Before like Wednesday next week. Going for 75/75....
14. (Original post by posthumus)
Ah okay, thank you for confirming that

Makes sense I guess since you might as well just have them both as one activity if you were going to portray it as a sort of "loop"
Hi

want to revise the defintions

Define:tree
15. (Original post by otrivine)
Hi

want to revise the defintions

Define:tree
Connected graph without any cycles.

Digraph ?
16. (Original post by posthumus)
Connected graph without any cycles.

Digraph ?
correct

digraph is if the graph is associated with the edges have a specific direction. directional graph
17. Can someone explain question 2b) in Exercise1F ? dont know how they got 15 (Edexcel book)
18. (Original post by OG-Ashley)
Can someone explain question 2b) in Exercise1F ? dont know how they got 15 (Edexcel book)
Just remember this : 0.5n(n-1)

"n" being the number of variable you have, so in this case that's 6
19. (Original post by posthumus)
Just remember this : 0.5n(n-1)

"n" being the number of variable you have, so in this case that's 6
Hi

Define: minimum spanning tree
20. (Original post by otrivine)
Hi

Define: minimum spanning tree
Erm a minimum spanning tree is where nodes have no more than 1 arc between them and there are no cycles. The weight of this tree will be the minimum ?

Define : Bipartite graph & Also maximum matching

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