배반사건 확률

${\mathrm{P}} ( A \cap B ) = 0$ $\displaystyle {\mathrm{P}} ( A ) = \frac{1}{6}$ ${\mathrm{P}} ( A \cup B ) = {\mathrm{P}} ( A ) + {\mathrm{P}} ( B )$ $\displaystyle \frac{1}{2} = \frac{1}{6} + {\mathrm{P}} ( B )$ $\displaystyle \therefore {\mathrm{P}} ( B ) = \frac{1}{2} - \frac{1}{6} = \frac{3 - 1}{6} = \frac{2}{6} = \frac{1}{3}$