A person writes 4 letters and addresses 4 envelopes. If the letters are placed at random in the envelopes, then the probability that all the letters are not placed in the right envelopes is

Given: A person writes four letters and addresses four envelopes.then,Number of ways in which four letter can be placed in four envelopes=factorial 4 or 4×3×2×1There is exactly one way in which all letter can go correctly. Required probability=4×3×2×1-14×3×2×1= 2324   Ans

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the letters can be kept in the envelops in 44 ways . but there is only one way to keep them in right places . so probability that all the letters are not placed in the right envelops =1/ 44
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