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EDEXCEL D1 Jan 01 question 6

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Aitch
It doesn't exactly make you feel super-confident about the board, does it?

I'd be extremely interested to see an official mark scheme for this paper you're doing. Oddly, it seems to be the only one which appears to be missing from all the usual sources. I don't think you can escape the logic of the "Max flow - min cut" theorem, anyway. You just have to show that the value of the above cut is 12 for it to follow that the maximum flow must also be 12.
If you do this in Part (e), perhaps it should follow that "See answer to part (e) below" gets you 6 marks for part (c)... strange question.

I have noticed that the papers are better structured and make more sense nearer to the present date so it should be okay.
Reply 21
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Aitch
2
Widowmaker
I have noticed that the papers are better structured and make more sense nearer to the present date so it should be okay.


I agree. I don't think Edexcel can afford another wrong D1 paper!
Reply 22
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Aitch
2
Surely some other D1 candidates must have done this paper? The lack of response at the top of the thread is worrying...

[...not worrying for you, Widowmaker... quite the opposite, if you're the only person doing any past papers! :cool: ]

Aitch
Reply 23
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samd
10
Woah that D1 Paper error story is scary. WTF are they playing at?

(This revision book which is endorsed by Edexcel is also packed with mistakes and silly questions)
Flows questions are horrible (I think) - I can never fit all the numbers on - they end up going all over the place, and I make silly mistakes when doing the labelling algorithm from a given flow pattern. AND, I can never find the cuts.
Reply 25
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Aitch
2
ljfrugn
Flows questions are horrible (I think) - I can never fit all the numbers on - they end up going all over the place, and I make silly mistakes when doing the labelling algorithm from a given flow pattern. AND, I can never find the cuts.


A good tip in looking for cuts is to try to include all the saturated arcs.
i love flow questions hold on while i find this question and get back to you

ok you use the three flow augmenting paths they give you - SAET, SBDT, SCFT

however there is not a cut that goes through all saturated arcs, therefore you just need to find a cut of Minimum Capacity, according to the min cut-max flow theory once you have found this minimum cut, the max flow will be of the same value

However - edexcel seem to have missed out labelling 2 of the arcs, which makes it diffcult to know wot to do with them haha

as far as i can see, although i may well be wrong - the min cut is of capacity 9 and therefore the same as the maximum flow
Reply 27
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Aitch
2
wicked_innit
i love flow questions hold on while i find this question and get back to you

ok you use the three flow augmenting paths they give you - SAET, SBDT, SCFT

however there is not a cut that goes through all saturated arcs, therefore you just need to find a cut of Minimum Capacity, according to the min cut-max flow theory once you have found this minimum cut, the max flow will be of the same value

However - edexcel seem to have missed out labelling 2 of the arcs, which makes it diffcult to know wot to do with them haha

as far as i can see, although i may well be wrong - the min cut is of capacity 9 and therefore the same as the maximum flow


There is a cut which passes through the saturated arcs. See above:

min. cut = max. flow = 12

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