A bag contains $3$ red and $5$ black balls and a second bag contains $6$ red and $4$ black balls. A ball is drawn from each bag. The probability that one is red and other is black, is
$\frac{3}{{20}}$
$\frac{{21}}{{40}}$
$\frac{3}{8}$
None of these
Three coins are tossed once. Find the probability of getting at most $2$ heads.
If $\frac{2}{11}$ is the probability of an event, what is the probability of the event $'$ not $A ^{\prime}$.
If $A$ and $B$ are mutually exclusive events, then the value of $P (A$ or $B$) is
Three houses are available in a locality. Three persons apply for the houses. Each applies for one house without consulting others. The probability that all the three apply for the same house is
Three coins are tossed once. Find the probability of getting no head.