Question
Average of 12 observations calculated by a student was
60 but when he again went through his observations he realised that he took value of three observations as 45, 60 and 42 in place of 70, 57 and 48 respectively and also realised that total observations taken by him was 11. Find the original average of all observations taken by him.Solution
Sum of 12 observations = 12 × 60 = 720 Original average = {720 + (70 + 57 + 48) - (45 + 60 + 42)}/11 = 748/11 = 68
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