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

Question

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

Options:

A . 30

B . 30.1

C . 29

D . 31

Answer: Option D
:
D

20 \sum i = 1 (x_{i} - 30) = 20 = 20 \sum i = 1 x_{i} - 20 \times 30 = 20

\Rightarrow 20 \sum i = 1 x_{i} = 620. M e a n = \frac{20 \sum i = 1}{20} = \frac{620}{20} = 31.

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