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Edexcel S2 - 27th June 2016 AM watch

  • View Poll Results: How did you find the Edexcel S2 exam?
    Very hard
    145
    14.71%
    Hard
    331
    33.57%
    Normal
    293
    29.72%
    Easy
    152
    15.42%
    Very easy
    65
    6.59%

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    (Original post by exclamationmark)
    How did people get 225? I ended up solving the quadratic p^2 + 0.7p - 55.5 <0 something like that 🙈
    It was n and sqrt(n) so the roots of the quadratic are equal to the sqrt of n and then you square the positive one as sqrt(x)≥0
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    (Original post by Michaelj99)
    I just put 225 in the whole thing and it worked out to get the probability they showed, my friend put both in when u find the z values, and said you get negative z for 342.25 i think? you didn't really have to say why you picked what?
    Yeah I subbed back in and you do get -Z, somehow didn't think to take the other root :/ hoping I get 6/8 or so for method marks
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    (Original post by Michaelj99)
    I just put 225 in the whole thing and it worked out to get the probability they showed, my friend put both in when u find the z values, and said you get negative z for 342.25 i think? you didn't really have to say why you picked what?
    Basically 342.25 would have worked if you took the negative square root at the bottom but idk

    I think and hope it's 225 cause that worked flawlessly when i plugged it back in and it only asked for 1 value
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    Can someone please explain what I did wrong as I can't see it! I got n=271!

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    (Original post by lovecupcakes1997)
    [5,9]
    I did 5^2pi = 25pi and 9^2pi = 81pi
    Then i wrote [25pi,81pi]
    E(X) = 1/2(25pi+81pi)
    = 53pi
    That's exactly what I did, pretty sure we were wrong though :/ Oh well, hopefully at least 2 marks.
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    (Original post by gameofthrones1)
    Can someone please explain what I did wrong as I can't see it! I got n=271!

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    You expanded (55.5 - 0.2n)^2 incorrectly
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    Hey guys for the 8 mark question i got n=62 which i know is wrong, but i want to know how much marks you think i could get, because i made a mistake when squarerooting 0.16n so i didnt do the quadratic equation
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    (Original post by apzoe)
    Guys what values did you get for a, b and k?
    What did you get

    I only did k and b , b is 8 as given and k is 1/9

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    (Original post by gameofthrones1)
    Can someone please explain what I did wrong as I can't see it! I got n=271!

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    You've written 1.75 then changed it to 1.45
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    (Original post by exclamationmark)
    How did people get 225? I ended up solving the quadratic p^2 + 0.7p - 55.5 <0 something like that 🙈
    You get 555-2p=7sqrtp and if you square all of that then you got 4p^2 -2269p + 555^2 =0 and then if you solve it using the quadratic function you get two answers 225 and something else with a point 25 in and as you were finding n it had to be a whole number so 225 was the answer
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    (Original post by NamelessPersona)
    You expanded (55.5 - 0.2n)^2 incorrectly
    How many marks out of 8 do you think this would score, i made the same mistake :/
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    (Original post by yasamin3)
    Hey guys for the 8 mark question i got n=62 which i know is wrong, but i want to know how much marks you think i could get, because i made a mistake when squarerooting 0.16n so i didnt do the quadratic equation
    I would say 4, an M1 for using normal approx, an A1 for half cc, and an M1 and A1 for getting to 55.5-0.2n = 1.75*sqrt(0.16n)
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    (Original post by iipebblesii)
    You've written 1.75 then changed it to 1.45
    My handwriting is quite bad, its 1.75 still haha
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    (Original post by S14151)
    How many marks out of 8 do you think this would score, i made the same mistake :/
    I'd say at least 4 look at my previous post
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    (Original post by NamelessPersona)
    I would say 4, an M1 for using normal approx, an A1 for half cc, and an M1 and A1 for getting to 55.5-0.2n = 1.75*sqrt(0.16n)
    Not too bad, thanks!
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    (Original post by NamelessPersona)
    You expanded (55.5 - 0.2n)^2 incorrectly
    Did I? I thought we didn't have to treat them as bracketed?
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    (Original post by Michaelj99)
    I just put 225 in the whole thing and it worked out to get the probability they showed, my friend put both in when u find the z values, and said you get negative z for 342.25 i think? you didn't really have to say why you picked what?
    I got 342 too! is it wrong?
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    (Original post by gameofthrones1)
    Did I? I thought we didn't have to treat them as bracketed?
    If you square both sides you treat it as a bracket
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    how many marks out of 8 just for not appling the continuity correction? everything else was correct just my quadratic was -55 not -55.5
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    (Original post by kieran1119)
    You get 555-2p=7sqrtp and if you square all of that then you got 4p^2 -2269p + 555^2 =0 and then if you solve it using the quadratic function you get two answers 225 and something else with a point 25 in and as you were finding n it had to be a whole number so 225 was the answer
    Ah thank you, sorry, but how was the 2n derived? As I thought 1.75 (z value) = (55.5 - n) / (0.16n)^0.5
 
 
 
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