5 white balls and $k$ black balls are placed into a bin.  Two of the balls are drawn at random.  The probability that one of the drawn balls is white and the other is black is $\frac{10}{21}$.  Find the smallest possible value of $k$.
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<|im_start|>user
5 white balls and $k$ black balls are placed into a bin.  Two of the balls are drawn at random.  The probability that one of the drawn balls is white and the other is black is $\frac{10}{21}$.  Find the smallest possible value of $k$.
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user
2
5 white balls and $k$ black balls are placed into a bin.  Two of the balls are drawn at random.  The probability that one of the drawn balls is white and the other is black is $\frac{10}{21}$.  Find the smallest possible value of $k$.
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