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    Question

    The average of some natural numbers is 15. If 30

    is added to first number and 5 is subtracted from the last number the average becomes 17.5 then the number of natural number is ?
    A 10 Correct Answer Incorrect Answer
    B 30 Correct Answer Incorrect Answer
    C 20 Correct Answer Incorrect Answer
    D 15 Correct Answer Incorrect Answer

    Solution

    The average of n natural number = 15
    New average of n natural numbers = 17.5
    ATQ,
    (17.5) n = (15)n + 30 – 5
    17.5n – 15n = 25
    n = 10

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