Probability: find the probability of event B given that event A occurs My Problem,
Suppose a family has 2 children,
if one children is randomly selected and it is a girl then what is the probability of the second child to be a girl ?
Please help. Thanks

Let's work by definition of conditional probabilities:
Let A = first child is girl, and B = second child is girl.
$$P(B \mid A) = \frac{P(A \cap B) }{P(A)}= \frac{0.5 \times 0.5}{0.5}=0.5$$
