SOLUTION: 5. A bag contains four blue marbles, five green marbles, and three yellow marbles. How many blue marbles should you add to the bag so that the probability of drawing a blue marble

Question 864996: 5. A bag contains four blue marbles, five green marbles, and three yellow marbles. How many blue marbles should you add to the bag so that the probability of drawing a blue marble is 0.80?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A bag contains four blue marbles, five green marbles, and three yellow marbles. How many blue marbles should you add to the bag so that the probability of drawing a blue marble is 0.80?
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# of ways to succeed:: 4+x
# of possible choices:: (4+5+3+x)
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Equation:
(4+x)/(12+x) = 0.8
4+x = 0.8(12+x)
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4+x = 9.6 + 0.8x
0.2x = 5.6
2x = 56
x = 28 (# of blue to add)
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Why?
(4+28)/(12+28) = 32/40 = 4/5 = 0.8
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Cheers,
Stan H.
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