Turn on thread page Beta
    • Thread Starter
    Offline

    14
    ReputationRep:
    how did it go
    got 40 for the flows question
    that's all I remember

    oh and I think 20/3 for the z and y values after the second iteration in simplex
    Offline

    2
    ReputationRep:
    40's familiar
    ALLLLLL the past papers are easy compared to that pile of rubbish
    40/100 seems to be the mark I will end up with
    I just wanted to pick up my paper and rip it to shreds.
    Teachers saying ooo yer you should all easily get 100 on D1 ( :mad: )
    Ack what a moron!
    Offline

    15
    ReputationRep:
    Good exam. I guess i got fairly lucky as all my sorts of questions came up. Much easier than M3 at least.
    Both myself and the other FM candidate got 40 for the flows question.
    The third simplex table was not optimal and the profit was something like 1733+(1/3) too, IIRC.
    Offline

    2
    ReputationRep:
    lol guess our teacher was bad then!
    Yep we learn't the OCR sylabus for an Edexcel exam!
    Offline

    0
    ReputationRep:
    (Original post by Gaz031)
    Good exam. I guess i got fairly lucky as all my sorts of questions came up. Much easier than M3 at least.
    Both myself and the other FM candidate got 40 for the flows question.
    The third simplex table was not optimal and the profit was something like 1733+(1/3) too, IIRC.
    Yep.. thats all correct

    Only bits i was iffy on was: That algorithm you had to mention in the last part of the kruskals/prims question (2 i think?) - I said use dijkstra to find shortest path from either of the verticies of the laid paths to the shortest path found using prims/kruskals.
    And also the Route Inspection one (Q 5) I went for Eularian. .start at A end at A as A was already even (they didn't specify :'( - i think :confused: ) - is that right? Now that i think about it.. think it was A -H.. you need to make A and H odd

    Also in the way of answers.. the bin-packing one.. 5 bins.. and it was optimal..hmm..
    And the weight of best path to take was in the region if one thousand four hundred- can't remember it exactly but the weight of repeated edges was 240 - i hope

    I actually enjoyed that paper! :eek: - coming from someone who was dreading starting the revision of it about 3 days ago.

    I messed up the quick sort question.. missed out a number (162).. and re-did it all... completed the paper.. and had about 20-15 mins to spare - w00t

    If someone has trouble remembering the questions.. heres what i remember:

    1)a) Add the initial matchings
    1)b) Use Alternating Paths to find complete matching

    2)a) Why 2 dummies?
    2)b) Draw the activity network with the 2 dummies.

    3)a) Use Prim's and Kruskals Algorithms to find minimum spanning trees in the networks.. ensuring you highlight the order in which you added the paths.

    4)a) Sort into DESC using Quick Sort
    4)b) Use bin packing algorith to cut out of 1m pieces of wood

    5)a) Dijkstra's Algorithm to find best path from A to H
    5)b) Use Route Inspection to find the best path from A.. to A?

    6)a) Find the the max flow through three different paths
    6)b) Present these flows on a diagram
    6)c) Use flow-augumenting algorithm to get best flow
    6)d) Show this is the best flow.. (max flow-min cut)

    7)a) Write the constraints... and objective function
    7)b) Show the table given was the first iteration of the Simplex method
    7)c) Find the second iteration
    7)d) Write down the values of all variables in the second iteration...
    7)e) Is this (second iteration) the optimal solution ?

    End of Paper

    Think all of that is right.. but dont quote me on it.

    MdSalih
    Offline

    15
    ReputationRep:
    Only bits i was iffy on was: That algorithm you had to mention in the last part of the kruskals/prims question (2 i think?) - I said use dijkstra to find shortest path from either of the verticies of the laid paths to the shortest path found using prims/kruskals.
    Can you remind me about this? Was this were u had to edit the minimum spanning tree by taking into account the two paths already laid down?

    And also the Route Inspection one (Q 5) I went for Eularian. .start at A end at A as A was already even (they didn't specify :'( - i think :confused: ) - is that right? Now that i think about it.. think it was A -H.. you need to make A and H odd
    That's correct. The route inspection involves starting and finishing at the same vertex. It's not the route inspection problem if you start and finish at different vertices. Also, A was already even so theres no point making it odd or you're going to have to repeat things. Altogether you had to repeat 2 arcs.
    Offline

    0
    ReputationRep:
    Yes... they said they had already laid two paths... and you had to mention an algorithm to incorporate them into your path as economically as possible.

    MdSalih
    Offline

    15
    ReputationRep:
    (Original post by MdSalih)
    Yes... they said they had already laid two paths... and you had to mention an algorithm to incorporate them into your path as economically as possible.

    MdSalih
    I said to remove AB and FI vertices and replace them with two vertices, (ab) and (fi), connect the edges to (ab) or (fi), if 2 edges (ab) or (fi) to the same vertex then choose the one of minimum weight. Find a minimum spanning tree using Kruskals then change (ab) (fi) back into A, B, F and I.
    Offline

    0
    ReputationRep:
    did anyone get 389 for the shortest route on the dijkstra algorithm? and 1421 for the route inspection?
    Offline

    2
    ReputationRep:
    What an evil paper

    Im not even sure if I got a C!

    Bring on the summer resits
    Offline

    0
    ReputationRep:
    Yes, those figures sound correct

    MdSalih
    Offline

    0
    ReputationRep:
    I think i got 42 for the flow question, i used back flows though, dont know if ur right.

    I was well scared when i didnt get an optimal solution, kinda expected it to be.

    I get the same as u guys in the answers but my flow is different to everyones
    Offline

    15
    ReputationRep:
    (Original post by Adil Bhai)
    I think i got 42 for the flow question, i used back flows though, dont know if ur right.
    I was well scared when i didnt get an optimal solution, kinda expected it to be.
    I get the same as u guys in the answers but my flow is different to everyones
    I know i found a minimum cut of 40 and marked it on my diagram and tried to find a path from S to T but the cut was okay. Perhaps your paper had a typo error for one of the capacities or something as i'm not sure how you got 42.
    Anyone got the question paper?
    Did u get a min cut of 42?
    Offline

    0
    ReputationRep:
    (Original post by Gaz031)
    I know i found a minimum cut of 40 and marked it on my diagram and tried to find a path from S to T but the cut was okay. Perhaps your paper had a typo error for one of the capacities or something as i'm not sure how you got 42.
    Anyone got the question paper?
    Did u get a min cut of 42?
    Apparently they aren't allowed to give test papers to to students after exams (quoted from invilgilators at my college). Which I find a little weird.. only harm I see is passing on info to people who haven't sat the exam.. but surely we can recall the info from memory. Other than that its the whole tightass thing edexcel have have with their past papers... but technically we have payed for it, or have we just payed for the examination.. and the marking not the material hmmm anyway.

    I remember getting 40 as max flow.. i cut through a couple places.. got 40 as min

    MdSalih
    Offline

    0
    ReputationRep:
    Yeah i got the question paper with me, ill describe the flow

    s to a 25
    s to c 20
    s to b 9
    b to c 12
    a to c 14
    a to d 8
    c to d 2
    b to f 10
    c to f 7
    c to e 15
    e to f 3
    d to e 3
    e to t 11
    d to t 15
    f to t 21

    there u go!

    yeah i did get min cut 42
    Offline

    15
    ReputationRep:
    (Original post by Adil Bhai)
    Yeah i got the question paper with me, ill describe the flow

    s to a 25
    s to c 20
    s to b 9
    b to c 12
    a to c 14
    a to d 8
    c to d 2
    b to f 10
    c to f 7
    c to e 15
    e to f 3
    d to e 3
    e to t 11
    d to t 15
    f to t 21

    there u go!

    yeah i did get min cut 42
    Can you scan the question page so i can figure out where i went wrong? Thanks.

    Are these the capacities or the flow?

    Edit: If i'm still getting a max flow of 40, with flow augs of (SADT8),(SACDT2),(SACET11),(SACE FT1),(SCEFT2),(SBFT9),(SCFT7).
    What further flow aug can u add to this?
    • Thread Starter
    Offline

    14
    ReputationRep:
    you cant use a back flow if it makes the flow negative, you can only take from a edge that already has a flow going the right way. otherwise you would be going against the direction of the edge.

    for the example I said a network of pipes, each pipe has a water filter that only works in one direction. sneaky huh?
    Offline

    15
    ReputationRep:
    (Original post by mik1w)
    you cant use a back flow if it makes the flow negative, you can only take from a edge that already has a flow going the right way. otherwise you would be going against the direction of the edge.

    for the example I said a network of pipes, each pipe has a water filter that only works in one direction. sneaky huh?
    I said the flow of traffic along a system of one way streets (But in case they didnt like that one i added in brackets, alternatively the flow of water through pipes).

    I feel like i'm in limbo. I don't have my final exam (M2) until Friday and i can hardly justify starting D2/P5/P6 until after that. I guess i'll just do the review exercises again and revise Bio4 for June. Wish i could take M2 tomorrow and get it over with.
    I may as well go watch a DVD or something.
    Offline

    2
    ReputationRep:
    Discussion looks interesting..

    Can anyone get me a look at the paper?

    Aitch

    [D1 guru[?] - 100 UMS in June 04!]
    Offline

    0
    ReputationRep:
    (Original post by Adil Bhai)
    Yeah i got the question paper with me, ill describe the flow
    Can you Scan/Write in the question

    Thanks.
 
 
 
Turn on thread page Beta
Updated: January 19, 2005

University open days

  • University of East Anglia
    All Departments Open 13:00-17:00. Find out more about our diverse range of subject areas and career progression in the Arts & Humanities, Social Sciences, Medicine & Health Sciences, and the Sciences. Postgraduate
    Wed, 30 Jan '19
  • Solent University
    Careers in maritime Undergraduate
    Sat, 2 Feb '19
  • Sheffield Hallam University
    City and Collegiate Campus Undergraduate
    Sun, 3 Feb '19
Poll
Do you have a role model?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

Equations

Best calculators for A level Maths

Tips on which model to get

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.