A bag contains 8 white and some black balls. If the probability of drawing a black ball from the bag is twice that of drawing a white ball, find the number of black balls in the bag.
Number of white balls = 8 Let x be the number of black balls. Total number of balls in the bag = 8 + x Also, the probability of drawing a black ball from the bag is twice that of drawing a white ball. ⇒ x/(8 + x) = 2 [8/(8 + x)] ⇒ x = 2 × 8 = 16 Hence, the number of black balls in the bag = 16
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