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    Question

    A bag contains red, blue, and green balls in the ratio

    of 2:4:5. If two balls are randomly selected from the bag, the probability that both are blue is 1/8 . Determine the total number of balls in the bag.
    A 22 Correct Answer Incorrect Answer
    B 33 Correct Answer Incorrect Answer
    C 44 Correct Answer Incorrect Answer
    D 55 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Let the number of red, blue and green balls in the bag are 2x, 4x and 5x respectively. Total number of balls in the bag = 2x + 4x + 5x = 11x So according to question: 4xC2/11xC2 = 1/8 4x (4x – 1)/ 11x (11x – 1) = 1/8 (16x – 4)/ (121x – 11) = 1/8 128x – 32 = 121x – 11 7x = 21, x = 3 So the total number of balls in the bag = 33

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