독립사건 합사건

$\displaystyle \mathrm{P} \mathit{(} A ^{C} ) = \mathrm{P} \mathit{(} B ) = \frac{2}{5}$에서 $\displaystyle \mathrm{P} \mathit{(} A ) = 1 - \mathrm{P} \mathit{(} A ^{C} ) = 1 - \frac{2}{5} = \frac{3}{5}$ 두 사건 $A$와 $B$는 서로 독립이므로 $\displaystyle {\mathrm{P}} ( A \cap B ) = {\mathrm{P}} ( A ) \times {\mathrm{P}} ( B ) = \frac{3}{5} \times \frac{2}{5} = \frac{6}{25}$ ${\mathrm{P}} ( A \cup B ) = {\mathrm{P}} ( A ) + {\mathrm{P}} ( B ) - {\mathrm{P}} ( A \cap B )$ $\displaystyle = \frac{3}{5} + \frac{2}{5} - \frac{6}{25}$$\displaystyle = \frac{19}{25}$