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Math Help - probability questions not getting answers

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    probability questions not getting answers

    1) What is the probability that the last three digits of a randomly selected phone number are all prime? Express your answer as a common fraction

    2) The sum of the digits of a number is 9. What is the probability that the number is prime?
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  2. #2
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    Quote Originally Posted by sri340 View Post
    1) What is the probability that the last three digits of a randomly selected phone number are all prime? Express your answer as a common fraction

    2) The sum of the digits of a number is 9. What is the probability that the number is prime?
    1) There are four prime digits: 2,~3,~5,~\&~7.
    Picking a digit at random there is \frac{4}{10} probability that it is prime.
    Now you finish.

    2) If the sum of the digits is multiple of nine then the number is divisible by nine.
    What does tell you?
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