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14.Probability
medium
$A$ and $B$ are two independent events. The probability that both $A$ and $B$ occur is $\frac{1}{6}$ and the probability that neither of them occurs is $\frac{1}{3}$. Then the probability of the two events are respectively
A
$\frac{1}{2}$ and $\frac{1}{3}$
B
$\frac{1}{5}$ and $\frac{1}{6}$
C
$\frac{1}{2}$ and $\frac{1}{6}$
D
$\frac{2}{3}$ and $\frac{1}{4}$
Solution
(a) $P(A \cap B) = P(A).P(B) = \frac{1}{6}$
$P(\bar A \cap \bar B) = \frac{1}{3} = 1 – P(A \cup B)$
$ \Rightarrow \frac{1}{3} = 1 – [P(A) + P(B)] + \frac{1}{6} $
$\Rightarrow P(A) + P(B) = \frac{5}{6}.$
Hence $P(A)$ and $P(B)$ are $\frac{1}{2}$ and $\frac{1}{3}.$
Standard 11
Mathematics