$A$ pair of fair dice is thrown independently three times. The probability of getting a score of exactly $9$ twice 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 $0.9$.

$A$ dice is thrown $10$ times. If getting an even number is considered as a success,then the probability of $4$ successes is:

$A$ binary number is made up of $16$ bits. The probability of an incorrect bit appearing is $p$ and the errors in different bits are independent of one another. The probability of forming an incorrect number is

$A$ random variable $X$ has a probability mass function $P(X=x) = \frac{{}^4C_x}{2^4}$ for $x = 0, 1, 2, 3, 4$. If $\mu$ and $\sigma^2$ are the mean and variance of the random variable $X$ respectively,then:

It is observed that there will be $25$ blood specimens of normal persons,if $100$ blood samples are tested. If $10$ specimens are sent to a laboratory for testing,then the probability of having at least two specimens of normal persons is