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    Question

    20 pens are there in a box where 8 are red pens, ā€˜p’

    are blue pens and remaining are black pens. If a pen is picked, the probability of getting blue pen is 0.5. Find the ratio of the number of blue pens and black pens.
    A 5:2 Correct Answer Incorrect Answer
    B 3:5 Correct Answer Incorrect Answer
    C 6:7 Correct Answer Incorrect Answer
    D 5:1 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Probability of getting a blueĀ  pen , => p/20 = 1/2 => p = 10 So, number of blackĀ  pensĀ  = 20 – 8 – 10 = 2 Required ratio = 10 : 2 = 5:1

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