$A$ box contains $15$ green and $10$ yellow balls. If $10$ balls are randomly drawn,one by one,with replacement,then the variance of the number of green balls drawn is

Two cards are drawn successively with replacement from a well-shuffled pack of $52$ cards. Let $X$ denote the random variable of the number of jacks obtained in the two drawn cards. Then $P(X=1) + P(X=2)$ equals

$A$ manufacturer of locks knows that $2 \%$ of his product is defective. If he sells the locks in boxes each with $100$ locks and guarantees that not more than $2$ locks will be defective in a box,then the probability that a box will fail to meet the guaranteed quality is

In a bombing attack,there is a $50 \%$ chance that a bomb will hit the target. At least two independent hits are required to destroy the target completely. Then the minimum number of bombs that must be dropped to ensure that there is at least a $99 \%$ chance of completely destroying the target is:

Suppose $X$ follows a binomial distribution with parameters $n$ and $p$,where $0 < p < 1$. If $\frac{P(X=r)}{P(X=n-r)}$ is independent of $n$ for every $r$,then $p$ is equal to

The probability that a person chosen at random is left-handed (in handwriting) is $0.1$. Then the probability that in a group of $10$ people there is exactly one left-handed person is: