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If-two-events-A-and-B-are-such-that-P-A-c-0-3-P-B-0-4-and-P-A-B-c-0-5-then-P-B-A-B-c-A-0-20-B-0-25-C-0-30-D-0-35-




Question Number 182695 by cortano1 last updated on 13/Dec/22
  If two events A and B are such     that P(A^c )=0.3 ; P(B)=0.4 and    P(A∩B^c )= 0.5 then P((B/(A∪B^c )))=?   (A) 0.20      (B) 0.25      (C) 0.30      (D) 0.35
$$\:\:\mathrm{If}\:\mathrm{two}\:\mathrm{events}\:\mathrm{A}\:\mathrm{and}\:\mathrm{B}\:\mathrm{are}\:\mathrm{such}\: \\ $$$$\:\:\mathrm{that}\:\mathrm{P}\left(\mathrm{A}^{\mathrm{c}} \right)=\mathrm{0}.\mathrm{3}\:;\:\mathrm{P}\left(\mathrm{B}\right)=\mathrm{0}.\mathrm{4}\:\mathrm{and} \\ $$$$\:\:\mathrm{P}\left(\mathrm{A}\cap\mathrm{B}^{\mathrm{c}} \right)=\:\mathrm{0}.\mathrm{5}\:\mathrm{then}\:\mathrm{P}\left(\frac{\mathrm{B}}{\mathrm{A}\cup\mathrm{B}^{\mathrm{c}} }\right)=? \\ $$$$\:\left(\mathrm{A}\right)\:\mathrm{0}.\mathrm{20}\:\:\:\:\:\:\left(\mathrm{B}\right)\:\mathrm{0}.\mathrm{25}\:\:\:\:\:\:\left(\mathrm{C}\right)\:\mathrm{0}.\mathrm{30}\:\:\:\:\:\:\left(\mathrm{D}\right)\:\mathrm{0}.\mathrm{35} \\ $$$$\:\: \\ $$
Commented by Acem last updated on 13/Dec/22
Hi friend!  What does A^c  mean?
$${Hi}\:{friend}! \\ $$$${What}\:{does}\:{A}\:^{{c}} \:{mean}? \\ $$
Commented by Emrice last updated on 13/Dec/22
  it is the conditional probability. and in our case here it is the probability of A knowing C.
$$ \\ $$it is the conditional probability. and in our case here it is the probability of A knowing C.
Answered by greougoury555 last updated on 14/Dec/22
 P(B/A∪B^(−) )= ((P(A∩B))/(P(A∪B^(−)  )))   = ((0.7−0.5)/(0.7+0.6−0.5)) = ((0.2)/(0.8)) = 0.25
$$\:{P}\left({B}/{A}\cup\overline {{B}}\right)=\:\frac{{P}\left({A}\cap{B}\right)}{{P}\left({A}\cup\overline {{B}}\:\right)} \\ $$$$\:=\:\frac{\mathrm{0}.\mathrm{7}−\mathrm{0}.\mathrm{5}}{\mathrm{0}.\mathrm{7}+\mathrm{0}.\mathrm{6}−\mathrm{0}.\mathrm{5}}\:=\:\frac{\mathrm{0}.\mathrm{2}}{\mathrm{0}.\mathrm{8}}\:=\:\mathrm{0}.\mathrm{25} \\ $$

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