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    Question

    The average number of novels on historical, thriller and

    fantasy in a library is 170, and the average number of novels on historical and fantasy is 140. If the number novels on fantasy is 20% less than the number of novels on thriller, then what is the number of novels on historical in the library?
    A 90 Correct Answer Incorrect Answer
    B 97 Correct Answer Incorrect Answer
    C 99 Correct Answer Incorrect Answer
    D 96 Correct Answer Incorrect Answer
    E 100 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 = 170 => x + y + z = 510 ….. (1) And, (x + z)/2 = 140 => x + z = 280 ….. (2) From equation 1 and 2 Number of novels on thriller = y = 230 Number of novels on fantasy = 0.8 × 230 = 184 Therefore, number of novels on historical = 510 – (230 + 184) = 96

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