SOLUTION: A bag contains x pink balls and y yellow balls. Three balls are radomly selected from the bag. a) Write and expression of the probability that three balls chossen were pink.

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Question 670555: A bag contains x pink balls and y yellow balls. Three balls are radomly selected from the bag.
a) Write and expression of the probability that three balls chossen were pink.
Is this right? Because i wansn't sure 3x/x+y ???
If there had been one more pink ball, then the probabilty that the three balls chosen were pink would have been double the answer found in a
b) show that y= x^2- x-2 / 5-x

Thanks for you help
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A bag contains x pink balls and y yellow balls. Three balls are radomly selected from the bag.
a) Write and expression of the probability that three balls chosen were pink.
Ans: [xC3]/[(x+y)C3]
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If there had been one more pink ball, then the probabilty that the three balls chosen were pink would have been double the answer found in a
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(x+1)C3/(x+y+1)C3 = 2[xC3]/(x+y)C3
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(x+1)C3/xC3 = 2(x+y+1)C3/(x+y)C3
(x+1)[xC3/xC3] = 2(x+y+1)[(x+y)C3/(x+y)C3]
(x+1) = 2(x+y+1)
x+1 = 2x+2y+2
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b) show that y= x^2- x-2 / 5-x
Note: That is not what I get as an answer.
Cheers,
Stan H.