help!!!!! Probability!!!

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A fair 6-sided die is rolled twice. The probability that the second roll is strictly less than the first roll can be written as a/b, where a and b are positive, coprime integers. What is the value of a+b?

  • help!!!!! Probability!!! -

    Assume die is fair.

    Rolling twice gives 36 outcomes, of which the second roll is strictly less than the first (successes) can be enumerated as follows:
    21,31,32,41,42,43,51,52,53,54,61,62,63,64,65
    Count how many successes there are, and divide by the size of the sample space (36).

  • help!!!!! Probability!!! -

    thanks sir...

  • help!!!!! Probability!!!::) -

    You're welcome!

    It would be even better if you would not use various aliases.

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