There are $n$ letters and $n$ addressed envelopes. The probability that each letter is placed in the correct envelope is

$A$ bag contains $5$ brown and $4$ white socks. $A$ man pulls out two socks. The probability that these are of the same colour is

Two cards are drawn at random from a pack of $52$ cards. The probability of these two being Aces is

If five-digit numbers are formed from the digits $0, 1, 2, 3, 4$ using every digit exactly once,then the probability that a randomly chosen number from those numbers is divisible by $4$ is:

$A$ box contains $10$ red balls and $15$ green balls. If two balls are drawn in succession without replacement,then the probability that one is red and the other is green is:

$5$ boys and $5$ girls are sitting in a row randomly. The probability that boys and girls sit alternatively is