Let $A$ be a set of all $4 -$digit natural numbers whose exactly one digit is $7 .$ Then the probability that a randomly chosen element of  $A$ leaves remainder $2$ when divided by $5$ is ..... .

If a coin be tossed $n$ times then probability that the head comes odd times is

Choose a number $n$ uniformly at random from the set $\{1,2, \ldots, 100\}$. Choose one of the first seven days of the year $2014$ at random and consider $n$ consecutive days starting from the chosen day. What is the probability that among the chosen $n$ days, the number of Sundays is different from the number of Mondays?

$A$ and $B$ are two events such that $P(A)=0.54$, $P(B)=0.69$ and $P(A \cap B)=0.35.$ Find $P ( A \cup B )$.

An experiment involves rolling a pair of dice and recording the numbers that come up. Describe the following events:

$A:$ the sum is greater than $8$,

$B : 2$ occurs on either die

$C:$ the sum is at least $ 7$ and a multiple of $3.$

Which pairs of these events are mutually exclusive ?

Three coins are tossed once. Find the probability of getting exactly $2$ tails.