New Enroll in RBI Grade B New Batch - Starts on May 21

    Question

    A bag holds 'a' red bands and 5 green bands. If two

    bands are drawn sequentially at random without replacement, the probability that both selected bands are red is given as 3/7 . Determine the value of 'a'.
    A 10 Correct Answer Incorrect Answer
    B 12 Correct Answer Incorrect Answer
    C 13 Correct Answer Incorrect Answer
    D 14 Correct Answer Incorrect Answer

    Solution

    ATQ, a*(a-1)/ [(a+5)*(a+4)] = 3/7 By using optional method, (10*9)/ (15*14) = 90/210 = 3/7 a = 10

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