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Edexcel S2 - 27th June 2016 AM watch

  • View Poll Results: How did you find the Edexcel S2 exam?
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    (Original post by SSD07)
    Attachment 556863Sorry i know this question has already been asked, but i just tried doing it myself and I'm a bit confused, its from June 2010.

    Basically i worked out that:
    2x+2y=20
    and because your trying to find P(Y>6)
    P(10-x>6) so therefore
    P(X<4) = 1/2 but why isn't this the answer? why do you have to add on a 1/6 as the answer is 2/3 ??
    please someone help
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    (Original post by SSD07)
    please someone help
    I need help with this too!!

    Posted from TSR Mobile
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    For the June 2015 paper, how do you do Q5 please????? Especially part D thank you!
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    (Original post by SeanFM)
    How do you find R in terms of X?

    (Hint: it is the area of a rectangle with one length being ... and the other ...)
    So it is length AP x BP = X(9-X) = 9X - X^2
    a= -1, B=9?
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    (Original post by NotNotBatman)
    So it is length AP x BP = X(9-X) = 9X - X^2
    a= -1, B=9?
    Correct (at least, that is what I would say too )
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    (Original post by SSD07)
    please someone help
    Consider both sides of the rectangle:
    Look at the method used for question 11:

    http://www.madasmaths.com/archive/ma...stribution.pdf
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    (Original post by SeanFM)
    Correct (at least, that is what I would say too )
    Okay, so I'm guessing E(R) is just the normal integral, but what are the limits, how are you supposed to work out the lower and upper limit of the area?
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    (Original post by NotNotBatman)
    Okay, so I'm guessing E(R) is just the normal integral, but what are the limits, how are you supposed to work out the lower and upper limit of the area?
    Use things from S1 - E(R) = E(aX^2 + bX) = E(aX^2) + E(bX) = aE(X^2) + bE(X).
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    PM for me, FP3's at the same time :unimpressed:

    Looking forward to this though, should be a nice one in comparison to the evil that has been the further papers so far...
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    (Original post by SeanFM)
    Use things from S1 - E(R) = E(aX^2 + bX) = E(aX^2) + E(bX) = aE(X^2) + bE(X).
    Hey I replied to you with my method on the previous page!
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    Name:  s2 mode.jpg
Views: 93
Size:  149.3 KB
    For part (b) why is the mode not 1?

    Surely 1/4*2^2 = 1 ?
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    (Original post by SeanFM)
    Use things from S1 - E(R) = E(aX^2 + bX) = E(aX^2) + E(bX) = aE(X^2) + bE(X).
    Got it, thanks!
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    (Original post by iMacJack)
    Hey I replied to you with my method on the previous page!
    Sorry - I didn't get that notification (I'd show you proof of that if you want, but feeling too lazy ) - notifications are bugged at the moment if you've noticed.

    You haven't integrated 3x/20 correctly, I think.
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    June 2014 (R) question 3d?

    https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

    I cant get my head around the differences wording in 3c and 3d.
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    (Original post by music with rocks)
    Name:  s2 mode.jpg
Views: 93
Size:  149.3 KB
    for part (b) why is the mode not 1?

    Surely 1/4*2^2 = 1 ?
     f(1) = (0.25) \times 1^2 = 0.25 .
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    (Original post by SeanFM)
     f(1) = (0.25) \times 1^2 = 0.25 .
    I am sorry but I don't understand what you are saying I am very confused haha
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    How would you answer this question - I have no idea how they got n/5 and the rest of the workings make no sense to me ! Can someone explain this throughly to me ? Name:  image.jpg
Views: 35
Size:  318.6 KB
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    (Original post by SeanFM)
    A distribution X is used to model the length, in mm, of the first tear of a uPhone charger, and the PDF is specified below. However, Wapple have been careless and have lost some key details of the PDF.

    kx(1-x) if  0 \leq x &lt; 0.5

    \frac{23}{40} - \frac{3x}{20} if    0.5 \leq x \leq b

    0 otherwise.

    a) Given that b is the minimum value greater than 0 such that f(b) = 0, find the value of b.

    b) Hence find the value of k.

    c) Find the expected length of the tear and the standard deviation.

    d) Find the interquartile range of the length of tears.

    e) Wapple send out an inspector to 5 random people who had asked for refunds. If the tear is longer than 1mm for at least 3 customers, all five will be refunded (ignoring systematic/human error). Find the probability, to 2 s.f, of Wapple giving a refund to a random group of 5 customers who have complained.
    Please could you post the answer for part c, I keep getting a decimal for the mean and not a fraction, thanks
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    https://57a324a1a586c5508d2813730734...%20Edexcel.pdf

    4e.
    How did they work out the lower quartile without subbing into the integration? Its only 1 mark so I assumed they havent done that also its not in the mark scheme.
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    (Original post by Music With Rocks)
    Name:  s2 mode.jpg
Views: 93
Size:  149.3 KB
    For part (b) why is the mode not 1?

    Surely 1/4*2^2 = 1 ?
    (Original post by Music With Rocks)
    I am sorry but I don't understand what you are saying I am very confused haha
    I'm not quite sure either you've asked about f(1) but then calculated f(2).
 
 
 
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