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    Question

    The average marks obtained by 20 students in a test is 74.

    It was later found that 78 was wrongly recorded as 87 and 69 was wrongly written as 63. What is the revised average?
    A 68.55 Correct Answer Incorrect Answer
    B 85.43 Correct Answer Incorrect Answer
    C 73.85 Correct Answer Incorrect Answer
    D 90.25 Correct Answer Incorrect Answer

    Solution

    ATQ,

    Correct average

    = {(20 ├Ч 74) тАУ 87 + 78 тАУ 63 + 69} / 20

    = {1480 тАУ 87 + 78 тАУ 63 + 69} / 20

    = 1480 тАУ 87 = 1393 + 78 = 1471 тАУ 63 = 1408 + 69 = 1477

    Correct average = 1477 / 20 = 73.85

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