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    Question

     A box contains 12 yellow marbles, ‘x’ blue marbles

    and 12 white marbles. A box contains 5 yellow marbles, 2 blue marbles and 3 white marbles. The probability of drawing a blue marble at random from the box is 1/7. If (x/2) blue marbles from the box are transferred to the bag, then find the probability of drawing a blue marble and a white marble from the box.
    A 4/21 Correct Answer Incorrect Answer
    B 7/31 Correct Answer Incorrect Answer
    C 2/11 Correct Answer Incorrect Answer
    D 9/25 Correct Answer Incorrect Answer

    Solution

    According to the question, x/ (12+ x + 12) = 1/7 => 6x = 24 => x = 4 Therefore, number of blue marbles transferred to bag = x/2 = 2 Total number of blue marbles in the box after the transfer = 2 + 2 = 4 Total number of marbles in the bag after the transfer = 5 + 2 + 3 + 2 = 12 Required probability = (4C1 × 3C1)/12C2 = 2/11

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