$A$ couple has two children. Find the probability that both children are males,if it is known that at least one of the children is male.

If $A$ and $B$ are two events such that $P(A) = \frac{3}{8}$,$P(B) = \frac{5}{8}$ and $P(A \cup B) = \frac{3}{4}$,then $P(A|B) = $

$A$ family has two children. What is the probability that both the children are boys given that at least one of them is a boy?

If $A$ and $B$ are two events such that $P(B) \neq 0$ and $P(B) \neq 1$,then $P(\bar{A} \mid \bar{B})$ is equal to:

Let $S$ be the sample space of all $3 \times 3$ matrices with entries from the set $\{0, 1\}$. Let the events $E_1$ and $E_2$ be given by $E_1 = \{A \in S : \operatorname{det} A = 0\}$ and $E_2 = \{A \in S : \text{sum of entries of } A \text{ is } 7\}$. If a matrix is chosen at random from $S$,then the conditional probability $P(E_1 \mid E_2)$ equals:

Let $X$ be a random variable which takes values $1, 2, 3, 4$ such that $P(X=r) = K r^3$ where $r = 1, 2, 3, 4$. Then: