When a fair die is rolled once,what is the probability of getting $1$ or $6$ on the top face?

The probability of hitting a target by three marksmen are $\frac{1}{2}, \frac{1}{3}$ and $\frac{1}{4}$ respectively. The probability that one and only one of them will hit the target when they fire simultaneously,is

The probability that $A$ speaks truth is $4/5$,while the probability that $B$ speaks truth is $3/4$. The probability that $A$ and $B$ contradict each other when asked to reveal the fact is

If $A$ is a sure event,then the value of $P(\text{not } A)$ is:

$A$ fair coin is tossed repeatedly. If a tail appears on the first four tosses,then the probability of a head appearing on the fifth toss equals:

Six faces of an unbiased die are numbered with $2, 3, 5, 7, 11$ and $13$. If two such dice are thrown, then the probability that the sum on the uppermost faces of the dice is an odd number is