# Oh, Probablility...Watch

#1
Given P(A)=.6, P(A B')=.4, and P(A B)=.85, Find the value of P(B).

I started by filling what was given into some formulae...

.85= .6 + P(B) - P(A B)
.4= .6+ P(B') - P(A B')

Am I on the right track?
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9 years ago
#2
B or P(B)?
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#3
(Original post by Kevin_B)
B or P(B)?
yeah, P(B), my mistake, I just edited.
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9 years ago
#4
P( A and B' ) is just the intersection of A without B, draw a venn diagram and you can find the intersection, then use P( A or B ) = P(A) + P(B) - P( A and B ). Is this edexcel?
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9 years ago
#5
(Original post by nk9230)
Given P(A)=.6, P(A B')=.4, and P(A B)=.85, Find the value of P(B).

I started by filling what was given into some formulae...

.85= .6 + P(B) - P(A B)
.4= .6+ P(B') - P(A B')

Am I on the right track?

First equation should be:

For your second equation I would look to express the probability of A in terms of the two subsets
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#6
(Original post by Kevin_B)
P( A and B' ) is just the intersection of A without B, draw a venn diagram and you can find the intersection, then use P( A or B ) = P(A) + P(B) - P( A and B ). Is this edexcel?
No, IB Maths SL.
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#7
(Original post by ghostwalker)
First equation should be:

For your second equation I would look to express the probability of A in terms of the two subsets
Yeah, I typed the equation in wrong , and How would I do that?
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