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9th Class Mathematics Probability Question Bank Probability

  • question_answer
    Find the probability that a number selected at random from the numbers 1 to 25 is not a prime number when each of the given numbers is equally likely to be selected.

    A)  \[\frac{9}{25}\]

    B)                                         \[\frac{16}{25}\]                             

    C)         \[\frac{11}{25}\]                                             

    D)         \[\frac{6}{25}\]

    Correct Answer: B

    Solution :

    \[S=\{1,2,3,4,........,25\}\] Let E= event of getting a prime number \[=\{2,3,5,7,11,13,17,19,23\}.\] Then, \[n(E)=9.\] \[\therefore \]\[P(E)=\frac{n(E)}{n(S)}=\frac{9}{25}\] Required probability \[=1-P(E)\] \[=\left( 1-\frac{9}{25} \right)=\frac{16}{25}\]


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