Question A bag contains 15 white and some black balls. If the probability of drawing a black ball from the bag is thrice that of drawing a white ball, find the number of black balls in the bag.
Video Explanation
Explanatory Answer
Bag contains 15 white balls
Let the bag contain ‘n’ black balls
Total number of balls = (15 + n)
Probability of drawing a black ball = \\frac{\text{number of black balls}}{\text{total number of balls}}) = \\frac{n}{(15 + n)})
Probability of drawing a white ball = \\frac{\text{number of white balls}}{\text{total number of balls}}) = \\frac{15}{(15 + n)})
Probability of drawing a black ball = 3(Probability of drawing a white ball)
i.e., \\frac{n}{(15 + n)}) = 3\(\frac{15}{15 + n}))
or n = 45
The number of black balls = 45.
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