Three coins are tossed. If at least one of them shows tail,then the probability that all three coins show tail is:

$A$ Chartered Accountant applies for a job in $2$ firms $X$ and $Y$. The probability of his being selected in firm $X$ is $0.7$,and being rejected at $Y$ is $0.5$,and the probability of at least $1$ of his applications being rejected is $0.6$. What is the probability that he will be selected in $1$ of the firms?

Two integers are chosen at random and multiplied. The probability that the product is an even integer is

$4$ coins are tossed once. Find the probability of $4$ tails.

An urn contains $25$ balls numbered $1$ to $25$. Suppose an odd number is considered a 'success'. $2$ balls are drawn from the urn with replacement. Find the probability of getting exactly $2$ successes.

From $21$ tickets numbered $1, 2, 3, \ldots, 21$,one ticket is drawn at random. Find the probability that the ticket drawn has a number divisible by $3$.