In a binomial distribution,the mean is $15$ and the variance is $10$. Then the parameter $n$ is:

The probability of a bomb hitting a bridge is $1/2$ and two direct hits are needed to destroy it. Find the least number of bombs required so that the probability of the bridge being destroyed is greater than $0.9$.

$A$ pair of dice is thrown $6$ times. What is the probability of getting a $4$ exactly seven times?

India and Pakistan play a $5$-test hockey series. What is the probability that India wins at least three games?

Let in a Binomial distribution,consisting of $5$ independent trials,probabilities of exactly $1$ and $2$ successes be $0.4096$ and $0.2048$ respectively. Then the probability of getting exactly $3$ successes is equal to ....... .

The random variable $X$ follows a binomial distribution $B(n, p)$ for which the difference between the mean and the variance is $1$. If $2 P(X=2) = 3 P(X=1)$,then $n^2 P(X > 1)$ is equal to $......$.