- #1
ArcanaNoir
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Homework Statement
A bowl contains w white balls. One ball is selected at random from the bowl; its color is noted, and it is returned to the bowl along with n additional balls of the same color. Another single ball is randomly selected from the bowl (now containing w+b-n balls) and it is observed that the ball is black. Show that the (conditional) probability that the first ball is selected was white is [itex] \frac{w}{w+b-n} [/itex]
(this is exactly how it is written by hand by my prof)
Homework Equations
I'm using "n" in between A and B as "intersect"
Well, probability of a, given b, is P(A|B)= [P(AnB)]/[P(B)]
I think (for independent events) P(AnB)=P(A)xP(B)
The Attempt at a Solution
I guess to me it should be w plus b PLUS n, not minus. And I'm not sure how to use conditional probability here, it looks more independent to me. Halp!