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Math Help - Probabiliy basic

  1. #1
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    Probabiliy basic

    If we flip a coin 6 times. What is the probability to get head exactly one time.

    so if we flip a coin one time it's 1/6,
    is it for fliping a coin 6 times also 1/6? because the events are independent?

    Another one;

    In a basket we have 10 white balls and 2 blue balls. Randomly we pick two balls.
    What is the probability that two balls are white?

    For picking one ball, and to be white is 10/12.
    For picking another ball, and to be white is 9/11.

    Is it the probability for two, just 9/11 or we have to add together something?

    Thank you for answers.
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  2. #2
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    Quote Originally Posted by Nforce View Post
    If we flip a coin 6 times. What is the probability to get head exactly one time.
    Another one;

    In a basket we have 10 white balls and 2 blue balls. Randomly we pick two balls.
    What is the probability that two balls are white?
    I am going to play the "back of the book" game with you.
    I give you the answer. But you must reply with the reasons.

    1) \dfrac{6}{2^6}.

    2) \dfrac{10}{12}\cdot\dfrac{9}{11}
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  3. #3
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    ok, the second answer I understand. 10/12 for the first event and 9/11 for the second for both 10/12 and 9/11 = 10/12 * 9/11

    but first I don't. maybe it's not obvious enough for me.

    When is going to be exactly 1?
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  4. #4
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    Quote Originally Posted by Nforce View Post
    ok, the second answer I understand. 10/12 for the first event and 9/11 for the second for both 10/12 and 9/11 = 10/12 * 9/11
    but first I don't. maybe it's not obvious enough for me.
    When is going to be exactly 1?
    We are going to have a sting of five T's and exactly one H.
    How many ways can this string TTHTTT be arranged?
    Now we get T\text{ or }H with equal probability, \frac{1}{2} six times.
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  5. #5
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    yes, now i understand.
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