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    Question

    The average of a set of 's' numbers is 20. If 80 is

    added to the set, then the average of the set becomes 20.5. Find the value of '4 X (s - 12)'.
    A 428 Correct Answer Incorrect Answer
    B 400 Correct Answer Incorrect Answer
    C 440 Correct Answer Incorrect Answer
    D 450 Correct Answer Incorrect Answer

    Solution

    Sum of all 's' numbers = 20s
    ATQ:
    (20s + 80) / (s + 1) = 20.5
    Multiplying both sides by (s + 1):
    20s + 80 = 20.5(s + 1)
    20s + 80 = 20.5s + 20.5
    80 - 20.5 = 20.5s - 20s
    59.5 = 0.5s
    s = 119
    4 X (s - 12):
    4 X (119 - 12) = 4 X 107 = 428

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