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JEE Main & Advanced Mathematics Permutations and Combinations Question Bank Definition of permutation, Number of permutations with or without repetition, Conditional permutations

  • question_answer
    In how many ways 3 letters can be posted in 4 letter-boxes, if all the letters are not posted in the same letter-box

    A) 63

    B) 60

    C) 77

    D) 81

    Correct Answer: B

    Solution :

    Three letters can be posted in 4 letter boxes in \[{{4}^{3}}=64\] ways but it consists the 4 ways that all letters may be posted in same box. Hence required ways = 60.


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