Question 601644: A bag contains five red and four blue tokens. A token is chosen at random, the colour recorded and the token is not replaced. A second token is chosen and the colour recorded. Find the probability that
a the second token is red given the first token is blue,
b the second token is blue given the first token is red,
c both tokens chosen are blue,
d one red token and one blue token are chosen
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! A bag contains five red and four blue tokens. A token is chosen at random, the colour recorded and the token is not replaced.
A second token is chosen and the colour recorded.
Find the probability that
a) the second token is red given the first token is blue:::
If the 1st is blue that leaves 5 red and 3 blue
Ans: 5/8
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b the second token is blue given the first token is red:::
If the 1st is red that leaves 4 red and 4 blue
Ans: 4/8 = 1/2
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c both tokens chosen are blue:::(4/9)*(3/8) = 1/6
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d one red token and one blue token are chosen
P(rb or br) = 1-(P(2red)+P(2blue))
= 1 - [(5/9)(4/8) + (1/6)]
= 1 - [(5/18)+(1/6)]
= 1 - [8/18]
= 1 - 4/9
= 5/9
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Cheers,
Stan H.
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