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Two balls are selected from a box containing 2 blue and 7 red balls. What is the probability that at least one ball is blue?
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Verified Answer
The correct answer is:
$\frac{2}{9}$
No. of blue balls $=2$ No. of red balls $=7$
Total no. of balls $=9$
Required probability $=P($ one ball is blue $)+P$ (both ball is blue)
$$
=\frac{2}{9} \times \frac{7}{8}+\frac{2}{9} \times \frac{1}{8}=\frac{14}{72}+\frac{2}{72}=\frac{16}{72}=\frac{2}{9}
$$
Total no. of balls $=9$
Required probability $=P($ one ball is blue $)+P$ (both ball is blue)
$$
=\frac{2}{9} \times \frac{7}{8}+\frac{2}{9} \times \frac{1}{8}=\frac{14}{72}+\frac{2}{72}=\frac{16}{72}=\frac{2}{9}
$$
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