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ACT probability question

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ACT probability question

by Night reader » Mon Dec 20, 2010 1:44 pm
A box contains 7 blue marbles, 4 red marbles and 6 green marbles. How many additional blue marbles must be added in the box so that the probability of randomly drawing a blue marble is 1/2?

A. 2
B. 3
C. 4
D. 5
E. 6

ACT questions might be well GMAT questions
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by anshumishra » Mon Dec 20, 2010 2:41 pm
Lets suppose, we need to add "x" blue balls,

So, (7+x)/(17+x) = 1/2
=> x =3.

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