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    Question

    There are 15 numbers such that average of first 12

    numbers is 20 while the average of last five numbers is 40. Find the 12th number, if the ratio between 11th and 12th number is 9:7, respectively.
    A 10.5 Correct Answer Incorrect Answer
    B 11.5 Correct Answer Incorrect Answer
    C 17.5 Correct Answer Incorrect Answer
    D 12.5 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Sum of first 12 numbers = (12 x 20) = 240 Sum of last 5 numbers = (40 x 5) = 200 Sum of 11th and 12th number = (240 - 200) = 40 So, 12th number = 40 x (7/16) = 17.5

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