JEE Main & Advanced Mathematics Probability Question Bank Definition of probability

  • question_answer
    Three letters are to be sent to different persons and addresses on the three envelopes are also written. Without looking at the addresses, the probability that the letters go into the right envelope is equal to [MNR 1982; MP PET 1990; Orissa JEE 2004]

    A)                 \[\frac{1}{27}\]    

    B)                 \[\frac{1}{9}\]

    C)                 \[\frac{4}{27}\]    

    D)                 \[\frac{1}{6}\]

    Correct Answer: D

    Solution :

               Total no. of ways placing 3 letters in three envelops \[=3\,!,\] out of these ways only one way is correct.                 Hence the required probability \[=\frac{1}{3\,!}=\frac{1}{6}.\]


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