Question:

A boy comes from a family of two children. What is the probability that the other child is his sister?

$\dfrac{1}{2}$

$\dfrac{1}{3}$

$\dfrac{2}{3}$

$\dfrac{1}{4}$

Step-by-Step Solution

Key Concept: Given one specific child is a boy, the other child is independently equally likely to be boy or girl.

$P=\dfrac{1}{2}$.

Correct Answer: 1