### The average of 9 observations was found to be 35. Later on, it was detected that an observation 81 was misread as 18. The correct average of the observation is.

A. 28 B. 42 C. 32 D. 45 Answer: Option B
$\begin{array}{l}\text{Difference = 81 – 18 = 63}\\ \text{So, change in average}\\ =+\frac{63}{9}\\ \text{ = + 7}\\ \text{Correct average = 35 + 7}=42\end{array}$