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    Question

    The average number of novels on historical, thriller and

    fantasy in a library is 30, and the average number of novels on historical and fantasy is 25. 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 20 Correct Answer Incorrect Answer
    B 25 Correct Answer Incorrect Answer
    C 31 Correct Answer Incorrect Answer
    D 14 Correct Answer Incorrect Answer
    E 18 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 = 30 => x + y + z = 90 ….. (1) And, (x + z)/2 = 25 => x + z = 50 ….. (2) From equation 1 and 2 Number of novels on thriller = y = 40 Number of novels on fantasy = 0.80 × 40 = 32 Therefore, number of novels on historical = 90 – (40 + 32) = 18

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