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    Two dice are rolled. Given that there is at least one six, what is the probability that both are sixes?

    The answer is 1/11. Can someone please explain how you come to this answer as i have no idea
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    bump
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    Its from a conditional probability worksheet
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    What can you get with two dice? How many of these situations have at least one 6, and how many have two 6s?

    (Original post by metaltron)
    The way I see it is you already have a 6. To get two sixes you must get a 6 on the second roll. This is P(get a six) on one die throw. However this does not give 1/11, so I'm not sure your answer is correct. Maybe somebody could confirm this.
    Don't think so.
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    nope its a normal dice.. theres another question that goes by A red and a blue die are rolled. Given that there is at least one six, what is the probability that the red die is showing six? -- the answer is 6/11
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    (Original post by FiGuev)
    nope its a normal dice.. theres another question that goes by A red and a blue die are rolled. Given that there is at least one six, what is the probability that the red die is showing six? -- the answer is 6/11
    See my first post to get the answer for this too.
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    (Original post by Slumpy)
    What can you get with two dice? How many of these situations have at least one 6, and how many have two 6s?



    Don't think so.
    Thank you for getting me out of a pickle. Hoping its fatigue after such a loooong hard day!
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    hang on I still dont understand
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    (Original post by FiGuev)
    hang on I still dont understand
    6*6 grid of possible results. How many squares have at least one 6? How many squares have 2 sixes?
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    ah i see
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    How would you have come to that answer using the formulas?
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    (Original post by Slumpy)
    6*6 grid of possible results. How many squares have at least one 6? How many squares have 2 sixes?
    please??
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    (Original post by FiGuev)
    How would you have come to that answer using the formulas?
     P(two \ sixes | at \ least \ one \ six \ obtained) = \frac{P(2 \ sixes)}{P(at \ least \ 1 \ six)} = \frac{P(2 \ sixes)}{1 - P(0 \ sixes)} = \frac{1/36}{11/36}
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    (Original post by FiGuev)
    How would you have come to that answer using the formulas?
    Depends what formulas you're talking about. You want P(two sixes|at least one six)=P(2 sixes)/P(at least one six), yes? Clearly the numerator is 1/36 - can you see how to calculate the denominator?
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    (Original post by Slumpy)
    Depends what formulas you're talking about. You want P(two sixes|at least one six)=P(2 sixes)/P(at least one six), yes? Clearly the numerator is 1/36 - can you see how to calculate the denominator?
    how do you calculate the denominator?
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    (Original post by lar di da)
    how do you calculate the denominator?
    See metaltron's post above mine.
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    (Original post by Slumpy)
    See metaltron's post above mine.
    I have, but i still dont get it. I haven't drawn out the 6*6 grid cause in an exam i just wouldn't' have time. how else would i work that there is at least one 6?
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    (Original post by lar di da)
    I have, but i still dont get it. I haven't drawn out the 6*6 grid cause in an exam i just wouldn't' have time. how else would i work that there is at least one 6?
    Metaltron's post (literally right above the one you quoted) doesn't even mention a 6*6 grid. Denominator=1-P(0sixes)=1-P(1st dice isn't a 6)*P(2nd dice isn't a 6)

    Edit - also, you'd never actually draw a 6*6 grid, you just need to think about it.
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    (Original post by Slumpy)
    Metaltron's post (literally right above the one you quoted) doesn't even mention a 6*6 grid. Denominator=1-P(0sixes)=1-P(1st dice isn't a 6)*P(2nd dice isn't a 6)

    Edit - also, you'd never actually draw a 6*6 grid, you just need to think about it.
    Oh i see. Okay its getting late and my brain seems dead but is 1 - P(0 sixes) the only way to work out that there is at least 1 six?
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    (Original post by lar di da)
    Oh i see. Okay its getting late and my brain seems dead but is 1 - P(0 sixes) the only way to work out that there is at least 1 six?
    Also never be afraid to draw a sample space diagram (the 6*6 grid) , they don't take as long as you think.
 
 
 
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