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If the algebraic sum of deviations of $20$ observations from $30$ is $20$ , then the mean of observations is
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The correct answer is:
$31$
$\sum_{i=1}^{20}\left(x_i-30\right)=20 \Rightarrow \sum_{i=1}^{20} x_i-20 \times 30=20$
$\Rightarrow \sum_{i=1}^{20} x_i=620$.
Mean $=\frac{\sum_{i=1}^{20} x_i}{20}=\frac{620}{20}=31$.
$\Rightarrow \sum_{i=1}^{20} x_i=620$.
Mean $=\frac{\sum_{i=1}^{20} x_i}{20}=\frac{620}{20}=31$.
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