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    Question

    The average number of novels on historical, thriller and

    fantasy in a library is 160, and the average number of novels on historical and fantasy is 155. If the number novels on fantasy is 30% less than the number of novels on thriller, then what is the number of novels on historical in the library?
    A 181 Correct Answer Incorrect Answer
    B 171 Correct Answer Incorrect Answer
    C 131 Correct Answer Incorrect Answer
    D 151 Correct Answer Incorrect Answer
    E 191 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 = 160 => x + y + z = 480 ….. (1) And, (x + z)/2 = 155 => x + z = 310 ….. (2) From equation 1 and 2 Number of novels on thriller = y = 170 Number of novels on fantasy = 0.7 × 170 = 119 Therefore, number of novels on historical = 480 – (170 + 119) = 191

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