Finding P(B) using complement and union rules

[huan.conchito]

Please help me with Probability

is this true in probability? P(AUB)' = (P(A) + P(B)) '

The question is
a) Assume that P(A) = 0.4 P(AnB)=0.1 P(A'nB')=0.2
P(B) = ?
what i did is:
P(AUB)= P(A)+P(B)- P(AnB)
P(AUB)= 0.4 + P(B)-0.1
P(A'nB')= 0.2 = P(AUB)' = 0.2 = 1 - (0.4 + P(B)-0.1)
P(B)= -0.5

NVM I GOT IT MYSELF

 

[marlon]

Only if A and B don't occur at the same time (simultaneously)

marlon

 

[huan.conchito]

what is the formula to manipulate such an expression if they occur at the same time?

 

[xanthym]

is this true in probability? P(AUB)' = (P(A) + P(B)) '

Here is the general form:
P{A ∪ B} = P{A} + P{B} - P{A ∩ B}


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