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    Question

    The average number of novels on historical, thriller and

    fantasy in a library is 40, and the average number of novels on historical and fantasy is 30. If the number novels on fantasy is 10% less than the number of novels on thriller, then what is the number of novels on historical in the library?
    A 3 Correct Answer Incorrect Answer
    B 2 Correct Answer Incorrect Answer
    C 6 Correct Answer Incorrect Answer
    D 7 Correct Answer Incorrect Answer
    E 10 Correct Answer Incorrect Answer

    Solution

    Let the number of novels on historical, thriller and fantasy be x, y and z respectively. Given, (x + y + z)/3 = 40 => x + y + z = 120 ….. (1) And, (x + z)/2 = 30 => x + z = 60 ….. (2) From equation 1 and 2 Number of novels on thriller = y = 60 Number of novels on fantasy = 0.90 × 60 = 54 Therefore, number of novels on historical = 120 – (60 + 54) = 6

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