SOLUTION: a box contains 4 white balls, one black ball and seven red balls. how many white balls must be added to the box so that the probability of drawing a white ball is 2/3

Question 711487: a box contains 4 white balls, one black ball and seven red balls. how many white balls must be added to the box so that the probability of drawing a white ball is 2/3
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
a box contains 4 white balls, one black ball and seven red balls. how many white balls must be added to the box so that the probability of drawing a white ball is 2/3
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# of white balls: 4 + x
Total # of balls (4 + 1 + 7 + x) = 12+x
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Equation:
(4+x)/(12+ x) = 2/3
12+3x = 24+2x
x = 12 (# of white balls to add to the box)
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Cheers,
Stan H.
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