There are n letters and n addressed envelopes. probability that all letters are not kept in right en

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14.Probability

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There are $n$ letters and $n$ addressed envelopes. The probability that all the letters are not kept in the right envelope, is

A

$\frac{1}{{n\,!}}$

B

$1 - \frac{1}{{n\,!}}$

C

$1 - \frac{1}{n}$

D

None of these

Solution

(b) Required probability is $1 – P$ (All letters in right envelope) $ = 1 – \frac{1}{{n\,!}}$

{As there are total number of $n\,!$ ways in which letters can take envelopes and just one way in which they have corresponding envelopes}.

Standard 11

Mathematics

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