Question
Average of 15 observations calculated by a student was
65 but when he again went through his observations he realised that he took value of three observations as 55, 60 and 50 in place of 86, 44 and 75 respectively and also realised that total observations taken by him was 14. Find the original average of all observations taken by him.Solution
Sum of 15 observations = 15 × 65 = 975 Original average = {975 + (86 + 44 + 75) - (55 + 60 + 50)}/14 = 1015/14 = 72.5
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