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    Question

    The average number of novels on historical, thriller and

    fantasy in a library is 120, and the average number of novels on historical and fantasy is 110. If the number novels on fantasy is 15% less than the number of novels on thriller, then what is the number of novels on historical in the library?
    A 100 Correct Answer Incorrect Answer
    B 121 Correct Answer Incorrect Answer
    C 101 Correct Answer Incorrect Answer
    D 91 Correct Answer Incorrect Answer
    E 81 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 = 120 => x + y + z = 360 ….. (1) And, (x + z)/2 = 110 => x + z = 220 ….. (2) From equation 1 and 2 Number of novels on thriller = y = 140 Number of novels on fantasy = 0.85 × 140 = 119 Therefore, number of novels on historical = 360 – (140 + 119) = 101

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