Probability
Conditional probability; 2-child problem
MMTS_Full_Test_02
Grade 12
Question:
A boy comes from a family of two children. What is the probability that the other child is his sister?
(A) $\dfrac{1}{2}$
(B) $\dfrac{1}{3}$
(C) $\dfrac{2}{3}$
(D) $\dfrac{1}{4}$
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: (A) $\dfrac{1}{2}$