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Manager
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The probability of pulling a black ball out of a glass jar [#permalink]
 13 Mar 2005, 14:02
The probability of pulling a black ball out of a glass jar is 1/X. The probability of pulling a black ball out of a glass jar and breaking the jar is 1/Y. What is the probability of breaking the jar?
a) 1/(XY).
b) X/Y.
c) Y/X.
d) 1/(X+Y).
e) 1/(X-Y).
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Manager
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P(A And B) = P(A).P(B|A)
Where P(A) = probability of being black
P(B) = Probabilty of breaking the jar
from the data in the prob, 1/y = (1/x) * P(B|A) = x/y.
Not sure if this is the right approach for this problem. As x/y gives the probability of breaking the jar given that a black ball is drawn from the jar.
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VP
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B too, same approach as prep_gmat
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GMAT Club Legend
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Let A denote P(pulling black ball out of glass jar)= 1/x
B denote P(black ball out of glass jar and breaking jar) = 1/y
C denote P(breaking glass jar)
A AND C = B
(1/x)(C) = 1/y
(C) = x/y
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Director
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P(A and B) = P(A).P(B)
X/Y
Last edited by vprabhala on 14 Mar 2005, 10:56, edited 1 time in total.
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SVP
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"B"
I think pulling a ball and breaking the jar r independent events so I don't think P(A|B) applies here.
For independent events:
P(A and B) = P(A).P(B)
1/Y = 1/X.P(B)
P(B) = X/Y
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Senior Manager
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X/y
prob of Blakc ball and Breaking jar= Prob of Black ball*prob of breaking jar=1/y
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