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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 Γ— 74) – 87 + 78 – 63 + 69} / 20

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

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

      Correct average = 1477 / 20 = 73.85

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