Question

Three letters are dictated to three persons & an envelope is addressed to each of them.the letters are inserted into the envelopes at random so that each envelope contains exactly one letter. find probability that at least one letter is in its proper envelope.

Answer 1

Let the 3 letters be identified as a, b and c.
The total number of arrangements of the letters is as follows:
a b c
a c b
b a c
b c a
c a b
c b a
Given that the envelopes are in the order a, b, c, can you see how many of the six possible arrangements will match at least one letter with the correct envelope?

Answer 2

what is prob ??????

Answer 3

In four out of the six possible arrangements at least one letter is matched with the correct envelope. So what is the probability of a match?