A) 9
B) 12
C) 15
D) 18
Correct Answer: D
Solution :
Since, root mean square ³ arithmetic mean \ \[\sqrt{\frac{\sum\limits_{i=1}^{n}{x_{i}^{2}}}{n}}\ge \frac{\sum\limits_{i=1}^{n}{{{x}_{i}}}}{n}=\sqrt{\frac{400}{n}}\ge \frac{80}{n}\Rightarrow n\ge 16\] Hence, possible value of n = 18.
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