The mean of 100 observations was calculated as 40. It was founder later on that one of the observation was misread as 83 instead of 53. The correct mean is :

A. 39

B. 39.7

C. 40.3

D. 42.7

$\begin{array}{l}\text{Difference = 53 – 83 = – 30}\\ \text{Change in average}\\ =-\frac{30}{100}\\ =-0.3\\ \text{So, correct average}\\ =40-0.3\\ =39.7\end{array}$