An unbiased coin is tossed $n$ times. If the probability of getting at least one head is greater than $0.8$,then the least value of $n$ is

Four fair dice are thrown independently $27$ times. Then the expected number of times,at least two dice show up a $3$ or a $5$ is

$A$ 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:

$A$ man tosses a coin $10$ times,scoring $1$ point for each head and $2$ points for each tail. Let $P(K)$ be the probability of scoring at least $K$ points. The largest value of $K$ such that $P(K) > \frac{1}{2}$ is

When employees with smart phones are randomly selected,$50 \%$ use them for office purpose. The probability that out of $10$ users exactly $2$ of them use for office purpose is

The mean and variance of a binomial variable $X$ are $2$ and $1$ respectively. The probability that $X$ takes values greater than $1$ is: