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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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