Five letters are placed at random in five addressed envelopes. The probability that all the letters are not…
Five letters are placed at random in five addressed envelopes. The probability that all the letters are not dispatched in the respective right envelopes is
$\frac{1}{120}$
$\frac{1}{5}$
$\frac{119}{120}$
$\frac{4}{5}$
Solution
The number of ways in which all the litters go to the correct envelope is 1
Probability that all letter go to correct envelope $=\frac{1}{5 !}$
Probability that all letter do not go to correct envelope $=1-\frac{1}{5 !}$
$=\frac{119}{120}$