Question

The mean of 50 observations is 39. If one of the observations which was 23 was replaced by 43, the resulting mean will be

• A. 39
• B. 40.6
• C. 39.4
• D. 38

Answer 1

The correct option is C 39.4

We know,
Mean = $\frac{Sumof50observations}{Numberofobservations}$

$\Rightarrow \text{Sum of 50 observations}=\text{Mean}\times \text{Sum of 50 observations}$
$=39\times 50=1950$
Given, one of the observations which was 23 was replaced by 43
Subtraction of old observation 23 and addition of new observation 43, we get sum of new observations
$\Rightarrow$ new sum = 1950-23+43
= 1970
$\therefore$ New mean = $\frac{1970}{50}=39.4$