1. avatar says

    good day Sir,

    please if i guess a different value from what you guessed will i still get the final answer including slack and the shadow price. and if not, what is the solution.

    • Profile photo of John Moffat says

      If you are meaning guessing a contribution in order to be able to draw the contribution line, then it won,t affect anything else at all. All we need is the angle/slope of the line and that will be the same whatever value of contribution you choose.
      I think it will be helpful for you to watch the lecture again.

    • Profile photo of John Moffat says

      The shadow price is the most extra that you would be prepared to pay for one extra unit of the limited resource.
      It is calculated by taking one extra unit and calculating the extra contribution that would be earned.
      If there is slack demand, it means that we are already producing less than the limit, so even if the limit on demand was increase by 1 to 11, we couldn’t produce any more and therefore could not make any more contribution.

  2. avatar says

    This lecture keeps stopping after 7 mins and will not play any further. I have watched the previous lectures with no issues.
    I have updated my flash player and cleared the history/cache etc and still stops at 7 mins – any ideas on what else I need to do – to be able to watch the lectures.


  3. avatar says

    Hi Sir,

    About shadow pricing, How the extra contribution is regarded wholly to the cost? If the contribution is in whole becoming the cost, there is no point to stretch the additional constraint. Because the benefit all becomes the cost.

    • Profile photo of John Moffat says

      What you say is true.
      That is why the shadow price is the most extra we are prepared to pay for one extra unit of the limited resource.
      So…..provided we can get it for less then it is worth having (because the total contribution will increase).

    • Profile photo of John Moffat says

      I did it for both labour and for material. However, since material is not a binding constraint the shadow price is obviously zero.

      In the exam you will be told which resources to calculate the shadow prices for.

    • Profile photo of John Moffat says

      You identify it by moving out the contribution line (keeping it parallel) as far as you can from the origin, without leaving the feasible region.

      (If you want me to answer questions, then please ask in the F5 Ask the ACCA Tutor Forum – it is not possible for me to always read all the comments beneath lectures :-) )

  4. Profile photo of John Moffat says

    There is no specific rule about how many decimal places (unless, obviously, the question specifies).
    Generally keep to two decimal places. It doesn’t matter if it impacts a later answer – the marks are for the workings, not for the final answer.

    (If you want me to answer a question, then please post it in the Ask the ACC Tutor forum – I cannot always read every comment under the lectures).

  5. avatar says

    hi prof moffat,
    i am practising the questions and got a problem. for those equations don’t give an integer, how many decimals shall we keep? i saw the exam bank kept two, but is it mandatory?since the value will impact the further calculation for the contribution and also shadow price. thank you very much for a clarification and thx for the great lectures as well!


  6. avatar says

    hi sir i was just wondering how come the demand is less than 10?because looking at the graph the demand line is also part of the feasible region.and when you did material and labour you said there was no slack because it on the labour and material line so how come there is slack for demand beacuase it is also part of the feasible region

    • avatar says

      For the above article I posted, on the second page i.e last paragraph, it says maximun amount of extra material required is 5000 kg (20000-15000), where did he get the 20000 from?

      • Profile photo of John Moffat says

        In the last paragraph (before workings) it explains that at point D they would be making 4000 units of Y.
        From the beginning of the example, we know that each unit of Y needs 5 kg of material.
        So….4000 units needs 20,000 kg.

  7. avatar says

    Thanks, the lecture was very insightful!
    Just a question though, at the end where you mentioned that shadow price for demand of E would be zero due to slack.
    What if that was not the case and demand is 10, I was wondering how would the calculation or approach be like?

      • Profile photo of John Moffat says

        If you look again at example 1 in the chapter, but this time suppose the maximum demand for executive chairs was 4 (instead of 10).
        The graph in the answer would stay the same except that the demand line would move to the left.
        It will mean that the feasible area will be A, D, O, and the point where the demand line crosses the labour line. (The existing point B would no longer be feasible).

        The new optimum point would be where the demand line crosses the labour line (which would be producing 4 executives and 32 standard chairs) and the new maximum contribution would be $312.
        This time, the material constraint would be redundant (and the shadow cost of material would be zero). However the demand would be limiting – if we could increase the maximum demand by 1 unit then we could change the production and make more contribution. The extra contribution from having demand for 1 more unit would be the shadow price.

  8. avatar says

    Dear Sir,
    I think your video cover all the complex area of the syllabus. But I found your examples as easy than compare to examination level or even in Kit. After having lectures I need to study from the study text and go through the examples which takes lots of time. Even I dont get time to have Kit questions. This way I can only cover 1 or 2 topics per week.

    The other question is that as I am very poor boy, so after completing my papers till f7. Will I be able to have any job? Which country do I go that is cheaper for students and can let me study with cheap costs and a job.

    Is there any solution? By the way Opentuition is a miracle for me.

    Many Thanks

    • Profile photo of John Moffat says

      The lectures do cover what you need for the exam in terms of the technique. The examples that I go through are certainly enough in terms of the technique, but the wording is deliberately kept more simple than the wording in the exam (because I am trying to make sure people understand the technique). Also exam questions often examine more than one topic in the same question – I can only teach one topic at a time in lectures :-)
      On courses, after I have finished the lecture the class then work through some past exam questions.
      If you look at the main Paper F5 page on this website you will find some lectures working through past exam questions – you might find this saves you time and saves you having to work through the Study Text so much.

      I cannot really help with regards to jobs and with regard to countries with cheap costs etc.. A lot depends on which country you live in. Courses are pretty expensive everywhere :-(

  9. avatar says

    Dear Sir,
    One question: The Point “B” that we gained, came from the simultaneous equation. I mean “2S+4E=80 and 5S+6E=180″. So why we used our graph for B? I mean if we simply could use this equation that was obvious from the question then why we need to put stress on graph? Then we cant certainly try the other farther points.

    • Profile photo of John Moffat says

      The problem is that if you did not have the graph then you would not know whether the optimal point was at point A, B, C or D. Depending on the angle of the objective/contribution line it could be any of them. Also, what about the point where the labour line crosses the demand line? This is not a feasible solution, but without the graph this would not be obvious.

      Also, in the exam you will almost certainly be required to draw the graph – in which case you obviously have no choice. (And on at least one occasion the graph was given in the question – in this case you obviously were not required to draw it yourself, but you did need to know how to interpret it.)

  10. avatar says

    Hi John,

    Good day to you :) I just started using opentuition for my study after June’13 exams. I thoroughly enjoyed your presentation in every chapter. Your delivery was so engaging. By any measure you are a very effective lecturer :) I appreciate your time, your patience and your ability to make a dry subject interesting :) Thank you so much, sir.

    I have already started doing revision. I’m using the latest BPP revision kit. I have something not understand about Linear Programming. I stuck in questions 24 (Question 3, December 2010 exam). In part (a), after draw the graph, we need to find the optimal solution using iso-contribution line then solving the simultaneous equations for these constraints :
    4x + 5y = 9,600 x 3
    3x + 2y = 5,000 x 4

    My questions is why we need to multiply the constraints by 3 for skilled labour constraints and multiply 4 for silk powder constraints? And why not multiply by 1 or 2? How we know when we need to multiply the constraints?

    Once again, thank you for your time and for always going the extra mile as a lecturer. I appreciate it more than you will ever know :)

    Enjoy your weekend :)

    • avatar says


      i bet people who ask these sort of questions haven’t even gone through all these video lectures..if you go one by one, you will see for yourself, how much this gets go..and you can make your own judgement if these are enough or not.

    • Profile photo of John Moffat says

      @sweetusudu, The notes do not cover every single thing in the syllabus, but they cover more than enough to pass. HOWEVER, you will only pass if you practice lots of questions – certainly all the past real exam questions, and preferably using one of the Revision/Exam Kits that are available.

  11. avatar says

    hai> sooooooooooo gud lect.i didnt hv any notes or relavant text buks for f5 and f6,bt i m gonna do exams this june.these lectures r it enough for exams?and dnt they gve graph papers for exams.if nt we couldnt get the accurate optimal solution? anyone pls help me 2 clear my doubts.thnx a lot for lectures.plz reply me soon.

  12. avatar says

    The linear programing lecture is quite well explained.However, can some one help me understand why I have failed to download the subsequent lecture to example 1. Thanks a lot.

  13. Profile photo of mapatel says

    at what point in the lecture does shadow pricing start, also I want to start in the middle of the lecture but it would not load when I click the area i want to start from,only shows me time at the bottom and circle keeps spinning as if its loading but it never starts.

  14. Profile photo of amoateng says

    Its really helpful and many thanks to open tuition. Honestly i was confused in class but after this great lecture, my mind is clear. God bless U(contents to the Lecturer). What’s the name of the lecturer?

  15. avatar says

    It is as gold for all business student. i have to be much interested in on line lectures. it is more helpful for all business student.i am most thankful for all ope tuition .com management.

  16. avatar says

    Hi there, this was helpful, however i am confused as to how 2 of the figures were calculated. They are:
    $152.50 for labour
    $22.50 for materials
    I can’t see how were these figures calculated. Could anyone help?
    Thank you

    • avatar says

      HI MAN !

      5s=181 – (6*4.75)
      5s= 152.5
      s=152.5/5 = 30.5.


      5s + 10e = 202.5
      (5s)+(6e)= (180)
      0 + 4e = 22.5
      e = 22.5/4 = 5.625.

      hope it s not too late

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