SOLUTION: Similar questions to this one were answered but I am not quite sure how to do this homework equation: An urn contains 3 red and 2 white numbered balls. A sample of 2 balls is ra

Question 441842: Similar questions to this one were answered but I am not quite sure how to do this homework equation:
An urn contains 3 red and 2 white numbered balls. A sample of 2 balls is randomly chosen.
15. Find the probability that the sample contains a red and a white ball (one digit after decimal point).
16. Find the expected number of white balls in the sample (one digit after decimal point).
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
An urn contains 3 red and 2 white numbered balls. A sample of 2 balls is randomly chosen.
15. Find the probability that the sample contains a red and a white ball (one digit after decimal point).
---
P(red/white) = 1 -{P(2red)+P(2white)]
P(red/white) = 1 - [(3C2+2C2)/5C2] = 1 -[4/10] = 0.6
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16. Find the expected number of white balls in the sample (one digit after decimal point).
--
P(no white) = 3C2/5C2 = 0.3
P(1 white) = 0.6
P(2 white) = 2C2/5C2 = 0.1
-----
E(white) = 0*0.3 + 1*0.6 + 2*0.1 = 0.8 white balls
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Cheers,
Stan H.

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