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Question: A person writes 4 letters and addresses 4 envelopes. If the letters are placed in the envelops at r...

A person writes 4 letters and addresses 4 envelopes. If the

letters are placed in the envelops at random, the probability

that not all letters are placed in correct envelopes is

A

1/24

B

11/24

C

5/8

D

23/24

Answer

23/24

Explanation

Solution

Required probability = 1 – P (all the letters are put in correct envelops)

The number of the ways of putting the letters in the envelops = 4P4 = 4!

The number of ways of putting letters in correct envelops = 1

Required probability = 1 – 124\frac { 1 } { 24 } = 2324\frac { 23 } { 24 }