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    IB Math AAHL
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    Probability
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    Probability

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    IB: 4
    1

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    0 / 7

    Let R be the value of a roll on 6 sided dice is shown in the following table. The probability distribution for R can be modelled by the following table.

    r

    1

    2

    3

    4

    5

    6

    P(R=r)

    0.1

    0.1

    p

    q

    0.2

    0.2

    Sally rolls the dice 100 times, and records 25 rolls of 6.

    1. Explain why this is not inconsistent with the table.

      [1]

    Josh plays a game using this dice. He pays $4 to roll the dice, and earns back the value of his roll in dollars.

    1. Determine the value of p and the value of q such that the game is fair.

      [6]
    2

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    The masses, in grams, of chocolate bars produced by a factory can be modelled by a normal distribution with mean 100g and standard deviation 0.6g. A chocolate bar can only be packaged if its mass is greater than 99g, otherwise is it melted back into the production line.

    1. Find the probability that a randomly selected chocolate bar is packaged.

      [2]

    On a given day, the number of chocolate bars packaged is 5000.

    1. Estimate, to the nearest 10, the number of chocolate bars that are melted back that day.

      [3]
    2. Given that a bar has a mass of less than 101g, find the probability it will be melted down.

      [3]
    3

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    James is sitting a multiple choice exam with 15 questions. Each question has 3 answer choices, of which only one is correct.


    James randomly picks an answer on each question. Let X represent the number of questions James answers correctly.

    1. State whether X is discrete or continuous.

      [1]
    2. Write down the value of E(X).

      [1]
    3. Find the probability that

      1. X=7,

        [1]
      2. 3<X<10.

        [3]
    4

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    During a very difficult practice maths quiz, 40 high‑school students each received a mark out of 100.

    problem image
    1. Write down the median mark.

      [1]
    2. How many students scored 24 marks or less?

      [1]
    3. How many students scored more than 29 marks?

      [1]

    A passing score is 27 marks.

    1. Determine the probability that a student scored above 29 marks given that they passed the exam.

      [3]
    5

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    7

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    Lessons

    Feeling shaky on the material? Check out a lesson:

    Thumbnail for Probabilistic Events

    Theoretical and experimental probability, complementary events, expected number of outcomes, sample space

    Probabilistic Events
    Thumbnail for Combined Events

    Venn diagrams, intersection and union of events, conditional probability, independent events

    Combined Events (Plus Only)
    Thumbnail for Dependence

    Tree diagrams, selection with/without replacement, dependence

    Dependence (Plus Only)
    Thumbnail for Bayes' Theorem

    Bayes' theorem with 2 and 3 events, sum of conditional probabilities

    Bayes' Theorem (Plus Only)