The probability that an event does not happen in one trial is $0.8$. The probability that the event happens at most once in three trials is:

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

$A$ die is thrown $(2n+1)$ times. The probability of getting $1$ or $3$ or $4$ at most $n$ times on it is

$A$ coin is tossed $100$ times. What is the probability of getting a head an odd number of times?

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

An objective type test paper has $5$ questions. Out of these $5$ questions,$3$ questions have four options each $(a, b, c, d)$ with one option being the correct answer. The other $2$ questions have two options each,namely true and false. $A$ candidate randomly ticks the options. Then,the probability that he/she will tick the correct option in at least four questions,is