Two cards are drawn successively with replacement from a well-shuffled pack of $52$ cards. The mean of the number of tens is:

In a Binomial distribution $B(n, p)$,the sum and product of the mean and the variance are $5$ and $6$ respectively,then $6(n+p-q)=$

There are $6$ boxes labelled $B_1, B_2, \ldots, B_6$. In each trial,two fair dice $D_1, D_2$ are thrown. If $D_1$ shows $j$ and $D_2$ shows $k$,then $j$ balls are put into the box $B_k$. After $n$ trials,what is the probability that $B_1$ contains at most one ball?

If the half-life period of a substance is $5 \text{ years}$, then the total amount of the substance left after $15 \text{ years}$, when the initial amount is $64 \text{ g}$, is: (in $\text{g}$)

What is the probability of getting exactly $6$ heads when a coin is tossed $10$ times?

$A$ bag contains $4$ red and $3$ black balls. One ball is drawn and then replaced in the bag and the process is repeated. Let $X$ denote the number of times a black ball is drawn in $3$ draws. Assuming that at each draw each ball is equally likely to be selected,then the probability distribution of $X$ is given by: