The mean and variance of a random variable $X$ having a binomial distribution are $4$ and $2$ respectively,then $P(X = 1)$ is

Let $X \sim B(n, p)$. If $E(X) = 2$ and $Var(X) = 1$, then the probability of getting at most one success is .....

In an examination,there are $10$ true-false type questions. Out of $10$,a student can guess the answer of $4$ questions correctly with probability $\frac{3}{4}$ and the remaining $6$ questions correctly with probability $\frac{1}{4}$. If the probability that the student guesses the answers of exactly $8$ questions correctly out of $10$ is $\frac{27 k}{4^{10}}$,then $k$ is equal to

If $A$ and $B$ simultaneously toss one coin each,$50$ times,then the probability of not getting a tail on both the coins in any single toss is:

The variance of binomial distribution with variables $n=5, p=0.30$ is . . . . . . .

$A$ fair die is thrown $4$ times. If getting a prime number on the die is considered as a success, then the probability of getting no success at all is ...