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    8.106 = 10K ^ 100
    0.8106 = k^100
    (0.8106)^1/100 = K
    K = 0.9979023974
    1/2 Mo = Mo (0.9979023974)^t
    1/2 = 0.9979023974^t
    Ln (1/2) ÷ Ln (0.9979023974) = t
    T = 330
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    anyone remember the answer for the question that was like 'write in the form Ax+ b +c/ (xxxx)
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    (Original post by Adam_98)
    I got 7/35 which cancelled to 1/5
    Wasn't it 23/35?
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    (Original post by Viableplayground)
    thought the paper was very nice apart from that last question. Please can someone explain question 8
    Part a)

    2tanϴ = 3x

    Differentiating it implicitly

    2sec^2ϴ * (dϴ/dx) = 3

    (dϴ/dx) = 3/(2sec^2ϴ)
    = 3/(2(1+tan^2ϴ))
    = 3/(2+2tan^2ϴ)
    = 6/(4+4tan^2ϴ)

    And from the question tanϴ=3x/2
    Therefore tan^2ϴ = 9x^2/4
    Putting this into (dϴ/dx) gives

    (dϴ/dx) = 6/(4+4(9x^2/4))
    = 6/4+9x^2 as required

    Part b)

    You had to separate the variables. The first integral had to be done using by parts. The second was from part a, 1/6th of tan^-1(3x/2) because it was the integral of 1/4+9x^2. c came out as pi.
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    (Original post by koolgurl14)
    Hm i remember get lambda as 1 can't remember what mu was but I did try it on the 3 equations it worked
    I think mu was 1/2
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    (Original post by lgrg)
    anyone remember the answer for the question that was like 'write in the form ax+ b +c/ (xxxx)
    a = -3
    b= 2
    c = 9
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    (Original post by C0balt)
    It was when t=2/3 right, not when x=2/3
    Yes, my bad
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    (Original post by bartbarrow)
    Personal opinion for grade boundaries (Not that people wanted to hear a realistic set of boundaries for PC3...) I think the paper was overall about the same as last years difficulty wise except some of the questions this year wanted a bit more.

    This was made using previous years boundaries and comparing the paper to this years

    100 UMS - 66
    A* - 61
    A - 55
    B - 49
    C - 43
    I'm ok with that... But what were your 'realistic' predicted boundaries for c3??
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    i hope so ! i
    (Original post by m00ngrk)
    Same here, you'll possibly get all for ecw and maybe lose one at the end for final answer if you got it all right apart from using 3 instead of 6
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    (Original post by Yo12345)
    Wasn't it 23/35?
    Definitely 13/35
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    (Original post by Matt309)
    i got identical answers to you except last one because i couldn't do it
    Even identical for the vector questions?
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    Can someone please give a list of the questions and corresponing marks?
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    (Original post by cannuks76)
    Attachment 551864

    There ya go mate, anyone correct me if I'm wrong
    Ty! For some reason I read it wrong and got 8.016=100k^100 :'(
    Apart from that I did everything correctly, so shouldn't lose too many marks (hopefully)
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    (Original post by mickel_w)
    Not of the original value. That would mean an element would only ever have 2 half lives..
    I put 330 in the exam and this was my working, couldn't remember the decimals after 8 but that's how you do it I think
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    (Original post by milemed11)
    just realised i left 0 and 360 in for the trig 5 marker but the range was 0<x<360 lol
    ****
    • Welcome Squad
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    Welcome Squad
    (Original post by SunDun111)
    for the partial fractions question instead of writing the A and B in fractions I wrote it was -2.5 and 4.5 would i lose marks?
    You wouldn't lose marks for putting the answer(s) in a different format, they always have 'or equivalent' next to the answer on the mark scheme.

    The only occasion you may lose marks is if they ask for it in a specific format, but I'm pretty sure they didn't for that question.
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    Welcome Squad
    (Original post by Parhomus)
    For the last question I believe I got -3ycos3y-sin3y=1/6(tan^-1(3x/2))+pi
    Sam I remember checking if it was negative twice when I did it as integration by parts , we all got the same C though
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    (Original post by mickel_w)
    I'm ok with that... But what were your 'realistic' predicted boundaries for c3??
    I only call these realistic because people were calling for 50 to be an A in C3, which would put it a whole 7-8 marks below what it usually is - it wasn't *that* bad.
    C4
    100 UMS - 66
    A* - 61
    A - 55
    B - 49
    C - 43

    C3
    100 - 70 (maybe 69)
    A* - 62
    A - 55
    B - 51
    C - 46
    D - 41
    E - 36
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    yes..well except the last ones. i couldn't quite figure out the coordinates of c and d so i just left it , but i did for the other parts
    (Original post by Adam_98)
    Even identical for the vector questions?
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    Can anyone remember how many marks the binomial expansion question was?
 
 
 
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