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Edexcel D1 - 17th June, 2016 [Exam discussion]

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Original post by Beat
Does anyone else think that cascade charts/scheduling diagrams are worth more than 4 marks? Literally it takes me 10-15 minutes to draw them!


Practise to get it done quicker, but if it's in the middle of the paper, and there are many more marks to be earned, I would say skip it and come back to it when you've finished; if it's still taking you some time to do.
Whats the best way to approach question 3 (d) of the June 2013 R paper without making a mess in the answer booklet?
Original post by Glavien
So, for c y u p w h t a g wouldn't you just choose w as your middle letter and discard c-w as h is to the right of w, then carry on the algorithm. I'm guessing that is incorrect because the list is not in order, but it still works right?


You've missed my point completely: you can only look at one letter at a time So when looking at w you can't see the other letters. You therefore have no idea which side of w to find h unless they are in order. Try imagining the letters on separate pieces of paper, all in a pile. When you look at the middle one and find it is w, you can't see the other pieces of paper.
Original post by tiny hobbit
You've missed my point completely: you can only look at one letter at a time So when looking at w you can't see the other letters. You therefore have no idea which side of w to find h unless they are in order. Try imagining the letters on separate pieces of paper, all in a pile. When you look at the middle one and find it is w, you can't see the other pieces of paper.



Ohhhh yesss(light bulb moment) thanks I get it now!! :smile:
Please could anyone explain how to do question 6f on this paper https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/June%202015%20QP%20-%20D1%20Edexcel.pdf Thanks :smile:
Reply 65
Avatar for Psst.
Psst.
9
How long will it take me to teach this module from scratch?
Original post by economicss


y = kx is a line through the origin. It must not cross the feasible region, so imagine making this line steeper until it goes through the top left corner of the feasible region. What is the gradient of the line then?
Original post by tiny hobbit
y = kx is a line through the origin. It must not cross the feasible region, so imagine making this line steeper until it goes through the top left corner of the feasible region. What is the gradient of the line then?


Sorry I'm really struggling with it, when I attempted this I got x=3 and y=5 and so is it from there that I get 5/3? How did you know it would be the top left hand corner point? :smile: Thanks
Original post by economicss
Sorry I'm really struggling with it, when I attempted this I got x=3 and y=5 and so is it from there that I get 5/3? How did you know it would be the top left hand corner point? :smile: Thanks


The inequality is y <= kx. This means that we want the bit below the line. If the line has a very small gradient, i.e. below the current feasible region, there is no feasible region left.
Reply 69
Avatar for M_17
M_17
1
Original post by Glavien
Whats the best way to approach question 3 (d) of the June 2013 R paper without making a mess in the answer booklet?


Erm, pencil?
Virtually impossible to draw an activity network first time without making any errors.

Original post by Psst.
How long will it take me to teach this module from scratch?


I genuinely think it can be done in a couple of days. Follow the set procedure and you can't go wrong.
Original post by tiny hobbit
The inequality is y <= kx. This means that we want the bit below the line. If the line has a very small gradient, i.e. below the current feasible region, there is no feasible region left.


Ah I see, got it, thank you!
Please could someone explain how to do question 6c on this paper https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/January%202014%20(IAL)%20QP%20-%20D1%20Edexcel.pdf Thanks :smile:
Original post by economicss


x+y>=500 does not touch the feasible reason. You now need to slide the line up until it goes through P. So to find k, add the coordinates of P together (x + y).

If you slid the line any further, P would no longer be in the feasible region.
Original post by tiny hobbit
x+y>=500 does not touch the feasible reason. You now need to slide the line up until it goes through P. So to find k, add the coordinates of P together (x + y).

If you slid the line any further, P would no longer be in the feasible region.


Ah I see, thank you :smile:
For questns like 5b here https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/June%202015%20(IAL)%20QP%20-%20D1%20Edexcel.pdf is there a formula that can be applied at all, or do they just have to be worked out question by question? Thanks :smile:
Original post by economicss
For questns like 5b here https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/June%202015%20(IAL)%20QP%20-%20D1%20Edexcel.pdf is there a formula that can be applied at all, or do they just have to be worked out question by question? Thanks :smile:


It's only a small number, so just count. There are 6 edges that go into F, so that involves going in and out of F 3 times. Then you need to look at the repeated edges to see whether you have to go to F again.
Original post by tiny hobbit
It's only a small number, so just count. There are 6 edges that go into F, so that involves going in and out of F 3 times. Then you need to look at the repeated edges to see whether you have to go to F again.


Thanks for your help :smile:
Please can anyone explain question 5diii here https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/June%202015%20QP%20-%20D1%20Edexcel.pdf I get the first two parts, but I'm confused how to make a link between them? Thanks :smile:
I ****ing hate d1
Original post by economicss
Please can anyone explain question 5diii here https://d0247e65b1a6ead8e6286cd43803e643462f2b31.googledrive.com/host/0B1ZiqBksUHNYNlBRQkZFLXdQS0E/June%202015%20QP%20-%20D1%20Edexcel.pdf I get the first two parts, but I'm confused how to make a link between them? Thanks :smile:


The total number of arcs in a minimum spanning tree is always either equal to or less than the total number of arcs in the 'original' graph (hence the name 'minimum spanning' ). Knowing this we can make an inequality out of the previous two parts.

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