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Math Help - probability

  1. #1
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    probability

    a six faced die is so biased that it is twice as likely to show an even number as an odd number when thrown. it is thrown twice. what is the probability that the sum of 2 numbers thrown is even
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  2. #2
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    Ok, let's start like this

    even + even = ...
    odd + even = ...
    even + odd = ...
    odd + odd = ...
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  3. #3
    Super Member Random Variable's Avatar
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    Condition on the first throw.

    P(sum is even) = P(sum is even|first throw is even)*P(first throw is even) + P(sum is even|first throw is odd)*P(first throw is odd) = (2/3)*(2/3) + (1/3)*(1/3) = 5/9
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