SOLUTION: There are 20 black marbles and 16 white marbles in a container and no others. How many black marbles must be removed from the container so that the probability of randomly selecti

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Question 1043295: There are 20 black marbles and 16 white marbles in a container and no others. How many black marbles must be removed from the container so that the probability of randomly selecting a black marble from the container is 1/3 ?
A) 8 B) 12 C) 16 D) 20
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
There are 20 black marbles and 16 white marbles in a container and no others. How many black marbles must be removed from the container so that the probability of randomly selecting a black marble from the container is 1/3 ?
Remove "x" black from 20 black to get 20-x black marbles
Removing x marbles leaves (20+16-x) = 36-x total marbles
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Equation:
(20-x)/(36-x) = 1/3
60-3x = 36-x
2x = 60-36 = 24
x = 12
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Cheers,
Stan H.
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A) 8 B) 12 C) 16 D) 20