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

Answer: (D)

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