Question 141

The arithmetic mean of 100 observations is 10. Of these the arithmetic mean of the first 25 observations is 12 while that of the last 65 is 9. The arithmetic mean of the remaining 10 observationsis

Solution

Sum of all the 100 observations = 1000
Sum of the first 25 observations = 25*12 = 300
Sum of the last 65 observations = 65*9 = 585

Hence, the sum of the 10 observations between these 2 groups = 1000-300-585 = 115
Hence, the mean of these 10 observations = 115/10 = 11.5

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AP ICET 2017

The arithmetic mean of 100 observations is 10. Of these the arithmetic mean of the first 25 observations is 12 while that of the last 65 is 9. The arithmetic mean of the remaining 10 observationsis

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