Probability Question 329
Question: There are n letters and n addressed envelopes, the probability that all the letters are not kept in the right envelope, is
Options:
A) $ \frac{1}{n!} $
B) $ 1-\frac{1}{n!} $
C) $ 1-\frac{1}{n} $
D) None of these
Show Answer
Answer:
Correct Answer: B
Solution:
Probability of all the letters kept in the right envelope is $ \frac{1}{n!} $ ( $ \because $ Total letters = n) i.e., $ P=\frac{1}{n!} $
We know, if q is the term used for the probability of the letters which are not kept in the right envelope.
Then $ p+q=1\Rightarrow q=1-p=1-\frac{1}{n!}. $
BETA
