For $X \sim B(n, p)$,if $p=0.6$ and $E(X)=6$,then $\operatorname{Var}(X)=$

The probability that a missile hits a target successfully is $0.75$. In order to destroy the target completely,at least three successful hits are required. Then the minimum number of missiles that have to be fired so that the probability of completely destroying the target is $NOT$ less than $0.95$,is. . . . .

$A$ fair coin is tossed $100$ times. The probability of getting tails an odd number of times is

For an initial screening of an entrance exam,a candidate is given $50$ problems to solve. If the probability that the candidate can solve any problem is $\frac{4}{5}$,then the probability that he is unable to solve less than $2$ problems is:

The mean and variance of a binomial distribution are $5$ and $4$ respectively. Then what is $P(X=1)$?

The probability distribution of the number of doublets in four throws of a pair of dice is given by