Cho A, B là hai biến cố xung khắc. Biết P(A)=15P(A) = \dfrac{1}{5}P(A)=51, P(A∪B)=12P\left( {A \cup B} \right) = \dfrac{1}{2}P(A∪B)=21. Tính P(B).
35\dfrac{3}{5}53.
815\dfrac{8}{15}158.
115\dfrac{1}{15}151.
310\dfrac{3}{10}103.
P(B)=P(A∪B)−P(A)=12−15=310P\left( B \right) = P\left( {A \cup B} \right) - P\left( A \right) = \frac{1}{2} - \frac{1}{5} = \frac{3}{{10}}P(B)=P(A∪B)−P(A)=21−51=103.
