New SIDBI Grade A New Batch Starts on Nov 18

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    Question

    A bag contains 20 white and some black balls. If the probability of drawing a black ball from the bag is 1.3 times that of drawing a white ball, find the number of black balls in the bag.

    A 20 Correct Answer Incorrect Answer
    B 30 Correct Answer Incorrect Answer
    C 26 Correct Answer Incorrect Answer
    D 35 Correct Answer Incorrect Answer

    Solution

    Number of white balls = 20
    Let x be the number of black balls.
    Total number of balls in the bag = 20 + x
    Also, the probability of drawing a black ball from the bag is 1.3 times that of drawing a white ball.
    ⇒ x/(20 + x) = 1.3 [20/(20 + x)]
    ⇒ x = 1.3 × 20 = 26
    Hence, the number of black balls in the bag = 26

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