upteto17 q129

129The number of observations in a survey is 40. If the mean of the first 10 observations is 4.5 and that of remaining is 3.5, then the mean of the whole survey is

Option : C
Explanation : Given, number of observation in a survey is 40.
Sum of first 10 observation = 10 × 4.5 = 45
and sum of remain 30 observation = 3.5 × 30 = 105
Sum of 40 observation = 105 + 45 = 150
∴ Mean of 40 observation = 150/40 = 3.75

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