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Solving questions on probability

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    Q1 gambling game has 3 reels which rotate independently they stop randomly at pics of fruit. probability of lemon is 0.2. a prize is won if you get 3 lemons.

    someone gets 4 attempts. calc the prob that he fails on first 3 attempts and wins on fourth.

    Q2 throw 3 sixes to win. someone has 5 attempts. what is the prob that he looses 4 attempts and win fifth?

    Q3 box contains 20 chocs. 6 are dark, 10 are milk and 4 are white. he eats 3 taken at random. calc prob that 2 are plain and one is white.
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    (Original post by non)
    Q1 gambling game has 3 reels which rotate independently they stop randomly at pics of fruit. probability of lemon is 0.2. a prize is won if you get 3 lemons.

    someone gets 4 attempts. calc the prob that he fails on first 3 attempts and wins on fourth.
    What's the probability he fails on his first attempt?

    Q2 throw 3 sixes to win. someone has 5 attempts. what is the prob that he looses 4 attempts and win fifth?
    What's the probability of throwing 3 sixes?

    Q3 box contains 20 chocs. 6 are dark, 10 are milk and 4 are white. he eats 3 taken at random. calc prob that 2 are plain and one is white.
    saving this one for later
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    (Original post by sputum)
    What's the probability he fails on his first attempt?



    What's the probability of throwing 3 sixes?



    saving this one for later
    0.8

    125/216

    what do you mean?
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    (Original post by non)
    0.8
    yes. so what is the probability he fails three times in a row?

    125/216
    I'm not sure how you came up with this but I phrased the question badly.

    Actually the original question is not clear as to how many dice the guy is throwing, I was assuming three sixes from three dice.

    what do you mean?
    it's a bit more complicated because you can pick 2 plain and 1 white in more than one way.
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    (Original post by sputum)
    yes. so what is the probability he fails three times in a row?


    I'm not sure how you came up with this but I phrased the question badly.

    Actually the original question is not clear as to how many dice the guy is throwing, I was assuming three sixes from three dice.



    it's a bit more complicated because you can pick 2 plain and 1 white in more than one way.
    0.8x0.8x0.8?

    1/6 x 1/6 x 1/6

    Whats the best way to work out this question?
    And thanks for the help so far.
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    OK so the first one you multiply what you got so far by the probability of a win and you're done.

    The second one is easily done using the fact that the two probabilities sum to 1 (so the probability of a success is 1- the probability of a failure)

    The third one you can do in a few ways. Have you done combinations?
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    (Original post by sputum)
    OK so the first one you multiply what you got so far by the probability of a win and you're done.

    The second one is easily done using the fact that the two probabilities sum to 1 (so the probability of a success is 1- the probability of a failure)

    The third one you can do in a few ways. Have you done combinations?
    Is the probability of winning dice dice game 1/216? Because that's 1/6x1/6x1/6
    So 4 loses is 215/216x215/216x215/216x215x216?
    And one win so x 1/216

    You can make it up by one plain one plain one white
    One white one plain one plain
    Are there any other ways?

    Thanks for your help
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    bump
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    (Original post by non)
    Is the probability of winning dice dice game 1/216? Because that's 1/6x1/6x1/6
    So 4 loses is 215/216x215/216x215/216x215x216?
    And one win so x 1/216

    You can make it up by one plain one plain one white
    One white one plain one plain
    Are there any other ways?

    Thanks for your help

    Apart from a x needing to be a /

    yes

     \frac{215}{216} \times \frac{215}{216} \times \frac{215}{216} \times\frac{215}{216} \times\frac{1}{216}
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    does plain = dark
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    PPW
    PWP
    WPP

    each have the same probability

    work it out and x3
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    (Original post by TenOfThem)
    PPW
    PWP
    WPP

    each have the same probability

    work it out and x3
    thank you so much. so would it be. 6/20x6/20x4/20=144/8000 x3=0.054
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    (Original post by non)
    thank you so much. so would it be. 6/20x6/20x4/20=144/8000 x3=0.054
    The denominator needs to change as each time you chose one you have fewer to chose from
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    (Original post by TenOfThem)
    The denominator needs to change as each time you chose one you have fewer to chose from
    oh ok so its 6/20x5/19x4/18=120/6840 x3=0.053
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    (Original post by TenOfThem)
    The denominator needs to change as each time you chose one you have fewer to chose from
    just checking if my answer is correct above.
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    (Original post by non)
    just checking if my answer is correct above.

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