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    Question

    The average number of novels on historical, thriller and

    fantasy in a library is 150, 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 104 Correct Answer Incorrect Answer
    B 154 Correct Answer Incorrect Answer
    C 144 Correct Answer Incorrect Answer
    D 146 Correct Answer Incorrect Answer
    E 134 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 = 150 => x + y + z = 450 ….. (1) And, (x + z)/2 = 140 => x + z = 280 ….. (2) From equation 1 and 2 Number of novels on thriller = y = 170 Number of novels on fantasy = 0.8 × 170 = 136 Therefore, number of novels on historical = 450 – (170 + 136) = 144

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