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Math Help - Dice probability question... should be quick for you guys :)

  1. #1
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    Dice probability question... should be quick for you guys :)

    I realized after I posted the title, this would be much easier with coins. Sorry.

    Here is my question:

    If you had to flip heads to win and you could re-flip ONCE, if you didn't flip heads on the first attempt, what is the probability of flipping heads?

    Is it still 50/50 because the flip events are independent? Or is the probability higher of flipping heads if you can re-flip the first loss?

    Thank you.
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  2. #2
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    Quote Originally Posted by Jaystats View Post
    Here is my question:
    If you had to flip heads to win and you could re-flip ONCE, if you didn't flip heads on the first attempt, what is the probability of flipping heads
    The answer is \dfrac{3}{4}.
    The only way to not to win is to flip two tails.
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  3. #3
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    Wouldn't that be 2/3 then?

    Event 1. Flip heads - win
    Event 3 Flip tails, flip heads - Win
    Event 4 Flip tails flip tails lose.
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  4. #4
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    Quote Originally Posted by Jaystats View Post
    Wouldn't that be 2/3 then?
    Event 1. Flip heads - win
    Event 3 Flip tails, flip heads - Win
    Event 4 Flip tails flip tails lose.
    Nope.
    P(H\cup TH)=P(H)+P(TH)=\frac{1}{2}+\frac{1}{2}\frac{1}{2}=  \frac{3}{4}
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  5. #5
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    Thanks.
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