Urn 1 contains 2 white and 4 black balls and urn 2 contains 4 white and 4 black balls. If a ball is drawn at random from one of the two urns, what is the probability that it is a white ball?

Respuesta :

Answer:    [tex]\dfrac{5}{12}[/tex]

Step-by-step explanation:

Given : Urn 1 contains 2 white and 4 black balls and urn 2 contains 4 white and 4 black balls.

Total balls in Urn 1 = 6

Total balls in Urn 2 = 8

Probability of drawing white ball from Urn 1 = P(W |Urn 1) = [tex]\dfrac{2}{6}[/tex]

Probability of drawing white ball from Urn 2 = P(W |Urn 2)= [tex]\dfrac{4}{8}[/tex]

Then probability that Urn1 is chosen =P(Urn 1)[tex]=\dfrac{1}{2}[/tex]

Similarly , P(Urn 2)[tex]=\dfrac{1}{2}[/tex]

By Law of total probability :

P(White)= P(W |Urn 1) x P(Urn 1) +P(W |Urn 2) x P(Urn 12)

[tex]=\dfrac{2}{6}\times\dfrac{1}{2}+\dfrac{4}{8}\times\dfrac{1}{2}=\dfrac{5}{12}[/tex]

Hence, the probability that it is a white ball = [tex]\dfrac{5}{12}[/tex]

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