Question

If the algebraic sum of deviations of 20 observations from 30 is 20, then the mean of observations is

• A. 30
• B. 30.1
• C. 29
• D. 31

Answer 1

The correct option is D 31

$\sum _{i=1}^{20}(x_i-30)=20=\sum _{i=1}^{20}{x}_i-20\times 30=20$
$\Rightarrow \sum _{i=1}^{20}{x}_i=620.Mean=\frac{\sum _{i=1}^{20}}{20}=\frac{620}{20}=31.$