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Homework Help: Uniform distrubtion

  1. Dec 8, 2011 #1
    1. The problem statement, all variables and given/known data

    http://www.xtremepapers.com/Edexcel/Advanced%20Level/Mathematics/Subject%20Sorted/S2/Solomon/Solomon%20B.pdf [Broken]

    Questions 3c and 3d

    2. Relevant equations

    3. The attempt at a solution
    ok so for Qc) it must be between 6 and 10 cm from the bottom and 8 and 12 cm from the left

    d) it must be within a square 2 cm all the way around the outer full screen

    But I don't see how to calculate the answers - there are an infinite number of solutions
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Dec 8, 2011 #2
    Prefacing everything with "Assuming X and Y are independent"... and for extra deviousness, "and that the screen is 20cm x 16cm".

    For c), it occupies 1/5 of the horizontal distance and 1/4 of the vertical distance.

    For d), take a clue from above and work out the probability of a dot appearing in any 1 cm2 of the screen.
  4. Dec 8, 2011 #3
    ok so c) 1/20

    d) any 1 cm2 = 1/320
    (16*20)-(16*12) = 128
    1/320 * 128 = 2/5

    is that right?
  5. Dec 8, 2011 #4
    apart from needing some explanatory text, looks ok
  6. Dec 8, 2011 #5
    what explanatory text
  7. Dec 8, 2011 #6
    To quote the front page of the paper:

    Advice to Candidates
    You must show sufficient working to make your methods clear to an examiner.
    Answers without working will gain no credit.
  8. Dec 8, 2011 #7
    me sad
    but thanks for that!
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