Question
A bag contains 13 white and some black balls. If the probability of drawing a black ball from the bag is 3 times that of drawing a white ball, find the number of black balls in the bag.
Solution
Given, Number of white balls = 13 Let x be the number of black balls. Total number of balls in the bag = 13 + x Also, the probability of drawing a black ball from the bag is 3 times that of drawing a white ball. ⇒ x/(13 + x) = 3[13/(13 + x)] ⇒ x = 39 Hence, the number of black balls in the bag = 39.
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