$A$ 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:

The probability that a student is not a swimmer is $\frac{1}{5}$. The probability that out of $5$ students selected at random,$4$ are swimmers is:

The binomial distribution whose mean is $9$ and whose standard deviation is $\frac{3}{2}$ is equal to

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

$A$ student appeared in an examination consisting of $8$ true-false type questions. The student guesses the answers with equal probability. The smallest value of $n$,so that the probability of guessing at least $n$ correct answers is less than $\frac{1}{2}$,is:

The probability that a student is a singer is $\frac{1}{5}$. Then,the probability that $4$ students are singers out of $5$ students is . . . . . . .