Question

A king comes from a family of two children. What is the probability that his sibling is a sister?

• A. $\frac{1}{2}$
• B. $\frac{1}{3}$
• C. $\frac{2}{3}$
• D. $\frac{3}{4}$

Answer 1

The correct option is C

$\frac{2}{3}$

Since the king comes from a family of two children, the total possibilities are $(Boy,Boy),(Boy,Girl),(Girl,Boy),(Girl,Girl)$

Since one of the two children is already a king (Boy)

Therefore, sample space $=(Boy,Boy),(Boy,Girl),(Girl,Boy)$

Favorable outcome $=(Boy,Girl),(Girl,Boy)$

Therefore probability $=\frac{2}{3}$