A bag contains 9 black and 12 white balls. One ball is drawn at random. What is the probability that the ball drawn is black?

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Mathematician

9/21
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Trainer

total no. of balls is 21. the probability of one ball out of 21 ball is 21c1 now, the probability of black ball is 9c1/21c1 =9/21 =3/7 Thank you.
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Engineering Tutor

Total balls 9+12=21 Total black balls =9 ∴probability of drawing a black ball =9/21 =3/7.
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9/21
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