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    Question

    A box contains 5 red, 4 blue and 3 green balls. Two

    balls are drawn at random without replacement. Find the probability that the two balls are of different colours.
    A 47/66 Correct Answer Incorrect Answer
    B 37/55 Correct Answer Incorrect Answer
    C 77/31 Correct Answer Incorrect Answer
    D 87/20 Correct Answer Incorrect Answer

    Solution

    Total balls = 5 + 4 + 3 = 12 Total ways to choose 2 balls = 12C2 = 66 Unfavourable cases: both balls same colour. Red–red: 5C2 = 10 Blue–blue: 4C2 = 6 Green–green: 3C2 = 3 Total same-colour pairs = 10 + 6 + 3 = 19 So favourable pairs (different colours) = 66 āˆ’ 19 = 47 Required probability = 47/66.

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