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    Question

    Average of 17 numbers is 81. If the average of the first

    six and last eight numbers is 91.5 and 71.5 respectively, and if the ninth number is 20% more than the eighth number and the tenth number is (50/9)% less than the ninth number, then find the ninth number.
    A 50.7 Correct Answer Incorrect Answer
    B 91.8 Correct Answer Incorrect Answer
    C 11.45 Correct Answer Incorrect Answer
    D 37.9 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ, Let the eighth number be 10x. So, the ninth number = 1.20 × 10x = 12x. Tenth number = 850/9 × 1/100 × 12x = 34x/3. So, 10x + 12x + 34x/3 = 81 × 17 – 6 × 91.5 – 8 × 71.5 = 255. Or, 100x/3 = 255. Or, x = 7.65. So, the ninth number = 12 × 7.65 = 91.8.

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