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    I asked a similar question before but i cant seem to find that thread

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    For this question where did they get 2y>=2x + 9z from?
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    Also for this question (5.c)iii) - the last ques. Why is it ABDBCBA? I put ABDCBA :3

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    (Original post by kiiten)
    I asked a similar question before but i cant seem to find that thread

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    For this question where did they get 2y>=2x + 9z from?
    the total of all components is 6x + 9y + 12z

    the components of type A is 2x + 4y + 3z

    you want next to say 2x + 4y + 3z is greater than or equal to 40% of 6x + 9y + 12z
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    (Original post by the bear)
    the total of all components is 6x + 9y + 12z

    the components of type A is 2x + 4y + 3z

    you want next to say 2x + 4y + 3z is greater than or equal to 40% of 6x + 9y + 12z
    Yeah i got that:

    2x + 4y + 3z >= 0.4 (6x + 9y + 12z)

    But if you multiply by 5 you get:

    10x + 20y + 15z >= 6x + 9y + 12z
    11y >= -4x - 3z

    ?
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    (Original post by kiiten)
    Yeah i got that:

    2x + 4y + 3z >= 0.4 (6x + 9y + 12z)

    But if you multiply by 5 you get:

    10x + 20y + 15z >= 6x + 9y + 12z
    11y >= -4x - 3z

    ?
    0.4 is 2/5
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    (Original post by the bear)
    0.4 is 2/5
    ughghghfh yeah youre right i forgot about the 2. Thanks for reminding me

    so its:

    10x + 20y + 15z >= 12x + 18y + 24z
    2y >= 2x - 9z

    Do you have any ideas about the second question i posted?
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    (Original post by kiiten)
    ughghghfh yeah youre right i forgot about the 2. Thanks for reminding me

    so its:

    10x + 20y + 15z >= 12x + 18y + 24z
    2y >= 2x - 9z

    Do you have any ideas about the second question i posted?
    no
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    (Original post by kiiten)
    Also for this question (5.c)iii) - the last ques. Why is it ABDBCBA? I put ABDCA :3
    ABDBCBA is a shorter route than ABDCA but it isn't the same length as the route in c,(ii).

    (In fact the question seems very ill-posed - it's not possible for Xiong to both choose the shortest route and a route the same length as in c, (ii)).
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    (Original post by DFranklin)
    ABDBCBA is a shorter route than ABDCA but it isn't the same length as the route in c,(ii).

    (In fact the question seems very ill-posed - it's not possible for Xiong to both choose the shortest route and a route the same length as in c, (ii)).
    the answer to c)ii) is 106km

    ABDBCBA 20 + 15 + 15 + 18 + 18 + 20 = 106km
    ABDCBA 20 + 15 + 33 + 18 + 20 = 106km

    My answer still gets the same length, with an 'actual' route. So why is their's right and mine wrong?
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    (Original post by DFranklin)
    ABDBCBA is a shorter route than ABDCA but it isn't the same length as the route in c,(ii).

    (In fact the question seems very ill-posed - it's not possible for Xiong to both choose the shortest route and a route the same length as in c, (ii)).
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    ^ The markscheme if you need it for reference
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    (Original post by kiiten)
    the answer to c)ii) is 106km

    ABDBCBA 20 + 15 + 15 + 18 + 18 + 38 = 124km
    BA = 20, not 38, surely?
    ABDCBA 20 + 15 + 33 + 18 + 20 = 106km

    My answer still gets the same length, with an 'actual' route. So why is their's right and mine is wrong?
    Because BD according to the original graph takes 35km, not 33. (I also now understand a bit more what they are getting at; will teach me to read the whole question next time and not just the bit I'm asked about!) You need to provide a route in terms of the original graph.
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    (Original post by DFranklin)
    BA = 20, not 38, surely?
    ABDCBA 20 + 15 + 33 + 18 + 20 = 106km
    Yeah thats what i put: BA is 20, CBA = 38

    (Original post by DFranklin)
    Because BD according to the original graph takes 35km, not 33. (I also now understand a bit more what they are getting at; will teach me to read the whole question next time and not just the bit I'm asked about!) You need to provide a route in terms of the original graph.
    BD = 15???

    I have provided it in terms of the original though?
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    (Original post by kiiten)
    Yeah thats what i put: BA is 20, CBA = 38
    You wrote that:

    ABDBCBA 20 + 15 + 15 + 18 + 18 + 38 = 124km

    If you didn't mean that AB =20, BD = 15, DB = 15, ..., CB = 18, BA = 38, then I have no idea what that line of yours was supposed to mean.

    BD = 15???
    My bad: I meant CD (this is why I hate trying to answer questions with attachments that you can't actually look at while answering the question!).

    I have provided it in terms of the original though?
    In terms of the original, ABDCBA has length 20 + 15 + 35 + 18 + 20 = 108. It only becomes 106 when you replace DC with DBC (reducing the journey from D to C from 35 to 33).
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    (Original post by DFranklin)
    You wrote that:

    ABDBCBA 20 + 15 + 15 + 18 + 18 + 38 = 124km

    If you didn't mean that AB =20, BD = 15, DB = 15, ..., CB = 18, BA = 38, then I have no idea what that line of yours was supposed to mean.

    My bad: I meant CD (this is why I hate trying to answer questions with attachments that you can't actually look at while answering the question!).

    In terms of the original, ABDCBA has length 20 + 15 + 35 + 18 + 20 = 108. It only becomes 106 when you replace DC with DBC (reducing the journey from D to C from 35 to 33).
    Oops yeah that was my mistake - i thought you were referring to my route - not the one given in the markscheme.
    Yes - i wrote it wrong: BA = 20 (ill edit my post now).

    i guess you could open the image in a new tab the minimise both the tsr and image tab to fit on both screens?
    Ah that makes more sense - you mean DC = 35 but DBC = 33

    Ok i think i see it now - they replaced DC with DBC on my route to get an 'actual' route. Right?
    ABDCBA ----> ABDBCBA
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    (Original post by kiiten)
    Ah that makes more sense - you mean DC = 35 but DBC = 33

    Ok i think i see it now - they replaced DC with DBC on my route to get an 'actual' route. Right?
    ABDCBA ----> ABDBCBA
    Yes. (Although I confess I'm not at all familiar with how these questions are normally laid out).
 
 
 
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