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  • Perplex
    IB Math AASL
    /
    Probability
    /

    Problem Bank

    [Maximum mark: 8]

    Marisol takes one of two subway lines to work each morning, as illustrated in the tree diagram below.

    Let:

    • ​A​ represent taking line ​A,

    • ​B​ represent taking line ​B,

    • ​T​ represent arriving on time,

    • ​L​ represent arriving late.

    1. Complete the following tree diagram.

      <p>Marisol takes one of two subway lines to work each morning:</p><ul><li><p>She catches Line A with probability 25\tfrac{2}{5}52​; otherwise she catches Line B (probability 35\tfrac{3}{5}53​).</p></li><li><p>If she takes Line A, the probability she <strong>arrives on time</strong> is 34\tfrac{3}{4}43​ (and hence is late with probability 14\tfrac{1}{4}41​).</p></li><li><p>If she takes Line B, the probability she <strong>arrives on time</strong> is 13\tfrac{1}{3}31​ (and hence is late with probability 23\tfrac{2}{3}32​).</p></li></ul><p>Copy and complete the following tree diagram:</p><pre><code>pgsql</code></pre><p>CopyEdit</p>
      [1]
    2. Find the probability that Marisol catches Line ​A​ and is late.

      [1]
    3. Find the probability that Marisol is late on a given morning.

      [2]
    4. Given that Marisol is late, find the probability that she took Line ​A.

      [2]
    5. Over two consecutive workdays, find the probability that she is late at least once.

      [2]

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