Two dice are thrown $5$ times,and each time the sum of the numbers obtained being $5$ is considered a success. If the probability of having at least $4$ successes is $\frac{k}{3^{11}}$,then $k$ is equal to

If $X$ follows the Binomial distribution with parameters $n=6$ and $p$ and $9 P(X=4) = P(X=2)$,then $p$ is

Two cards are drawn at random one after the other with replacement from a pack of playing cards. If $X$ is the random variable denoting the number of ace cards drawn, then the mean of the probability distribution of $X$ is

$A$ and $B$ are playing a chess game with each other. The probability that $A$ wins the game is $0.6$,the probability that he loses is $0.3$,and the probability that it is a draw is $0.1$. If they play three games,what is the probability that $A$ wins at least two games?

There are $800$ families with four children in each family. Assuming an equal chance for every child to be a boy or a girl,the number of families expected to have children of both sexes is:

The maximum value of the variance of a Binomial distribution with parameters $n$ and $p$ is