If two numbers are selected at random from $20$ consecutive integers,what is the probability that their sum is odd?

$A$ committee of two persons is selected from two men and two women. What is the probability that the committee will have exactly one man?

$A$ total of $13$ people,consisting of $5$ women and $8$ men,have applied for a job. If $2$ people are to be selected from these $13$ people,what is the probability that at least one woman is selected?

Out of $3$ men,$2$ women,and $4$ children,if $4$ people are selected at random,what is the probability that exactly $2$ children are selected?

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

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