A bag contains 10 white and some black balls. If the probability of drawing a black ball from the bag is 2 times that of drawing a white ball, find the number of black balls in the bag.
Given, Number of white balls = 10 Let x be the number of black balls. Total number of balls in the bag = 10 + x Also, the probability of drawing a black ball from the bag is 1.8 times that of drawing a white ball. ⇒ x/(10 + x) = 2[10/(10 + x)] ⇒ x = 20 Hence, the number of black balls in the bag = 20.
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