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RAJASTHAN ­ PET Rajasthan PET Solved Paper-2002

  • question_answer
    From the positive integers, four integers are selected randomly and then multiplied, then the probability of getting the digit 1, 3, 5 or 7 at the first place is

    A)  \[\frac{16}{625}\]

    B)  \[\frac{8}{625}\]

    C)  \[\frac{10}{17}\]  

    D)  None of these

    Correct Answer: A

    Solution :

     Number of digits which can appear at unit place =10 \[\therefore \] \[n(S)=10\] In the multiplication of the four number to get 1, 3, 5 or 7 at the unit place, it is necessary that in every number unit's digit is 1, 3, 5 or 7. \[\therefore \] \[n(A)=4\] \[\therefore \] \[P(A)=\frac{4}{10}=\frac{2}{5}\] \[\therefore \] Required probability\[={{\left( \frac{2}{5} \right)}^{4}}=\frac{16}{625}\]


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