31- #30

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Source: — Data Sufficiency |

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by ratindasgupta » Sun Aug 19, 2007 9:49 pm
it's a dependent probabability question.

Let the total no be x.

If probability that both picked blue is 6/11, then the equation is
9/x + 8/(x-1) = 6/11

solving it, you get x = 12.