Posted by **Christina** on Wednesday, April 22, 2009 at 9:31pm.

If P(a)=1/5, P(A and B)= 1/8, what is P(b/a)

i dont get it is it the same way as finding p or b or is it something entirely different and how do you find it

- Algebra 2 -
**Reiny**, Wednesday, April 22, 2009 at 9:46pm
I think you are dealing with "conditional probability"

usually written as P(B│A) and read as

"the probability of B given A"

P(B│A) = P(A and B)/P(A)

= (1/8) / (1/5)

= 5/8

- Algebra 2 -
**Christina**, Wednesday, April 22, 2009 at 9:49pm
so it would be division then i would have to cross multiply right??? by the way thank you...Alot!

- Algebra 2 -
**Reiny**, Wednesday, April 22, 2009 at 10:08pm
You are dividing 2 fractions at the end

(1/8) / (1/5)

= (1/8) ÷ (1/5)

= (1/8)x(5/1)

= 5/8

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