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Math Help - Quick Dice /Probability Question

  1. #1
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    Quick Dice /Probability Question

    This one has my head spinning, could someone help me out on the following dice problem? I'm having difficulty figuring out whether or not this is a permutation or combination question.

    Thanks in advance!

    Suppose two 6-sided dice are rolled.

    What is the probability that the sum is divisible by 5 or exactly 12?
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  2. #2
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    Re: Quick Dice /Probability Question

    List all the possible outcomes, how many is there?

    What are the probabilites for rolling a 5,10 & 12?
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    Re: Quick Dice /Probability Question

    Quote Originally Posted by pickslides View Post
    List all the possible outcomes, how many is there?

    What are the probabilites for rolling a 5,10 & 12?
    Oh now I feel dumb,

    With 36 possible outcomes, I suppose it would be as simple as 3/36 = 0.0833. D'oh! Thanks very much for the nudge in the right direction.

    This problem may be slightly more complex, as it involves finding the mean of a discreet probability model,

    Suppose you roll a 6-sided die. If you roll a 2 you make $2, if you roll a 6 you make $3 and if you roll any other number you pay $0.5. How much money should you expect to make on average?

    I know the formula for finding the mean is as simple as adding the various outcomes times their respective probabilities. But I'm unsure as to how I am supposed to plug in the data from the question. Any ideas?
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    Re: Quick Dice /Probability Question

    Quote Originally Posted by Danny09 View Post

    With 36 possible outcomes, I suppose it would be as simple as 3/36 = 0.0833. D'oh! Thanks very much for the nudge in the right direction.
    Maybe there is more than 3, we have (1,4),(2,3),(3,2),(4,1),(4,6),(6,6),(6,4),(6,6)
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  5. #5
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    Re: Quick Dice /Probability Question

    Quote Originally Posted by Danny09 View Post

    Suppose you roll a 6-sided die. If you roll a 2 you make $2, if you roll a 6 you make $3 and if you roll any other number you pay $0.5. How much money should you expect to make on average?

    I know the formula for finding the mean is as simple as adding the various outcomes times their respective probabilities. But I'm unsure as to how I am supposed to plug in the data from the question. Any ideas?
    Expected Value would be 2*(1/6)+3*(1/6)-0.5*(4/6) can you see why?
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