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    Question

    Average of 20 observations calculated by a student was

    77 but when he again went through his observations he realised that he took value of three observations as 50, 64 and 45 in place of 90, 41 and 46 respectively and also realised that total observations taken by him was 19. Find the original average of all observations taken by him.
    A 82 Correct Answer Incorrect Answer
    B 78 Correct Answer Incorrect Answer
    C 79 Correct Answer Incorrect Answer
    D 80 Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    Sum of 20 observations = 20 × 77 = 1540 Original average = {1540 + (90 + 41 + 46) - (50 + 64 + 45)}/19 = 1540/19 = 82

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