Question

The following table shows the marks obtained by 5 students in a class. What is the average marks of the class?

$$\begin{array}{cc}\text{Marks}& \text{Frequency}\\ 98& 1\\ 65& 1\\ 88& 2\\ 54& 1\end{array}$$

• A. 76.6
• B. 77.6
• C. 78.6
• D. 78.9

Answer 1

The correct option is C

78.6

Consider the table given below.
$$\begin{array}{ccc}\text{Marks}\left({\text{x}}_{\text{i}}\right)& \text{Frequency}\left({\text{f}}_{\text{i}}\right)& {\text{x}}_{\text{i}}{\text{f}}_{\text{i}}\\ 98& 1& 98\\ 65& 1& 65\\ 88& 2& 176\\ 54& 1& 54\\ \text{Total}& \sum {\text{f}}_{\text{i}}=5& \sum {\text{x}}_{\text{i}}{\text{f}}_{\text{i}}=393\end{array}$$

The average of a dataset with observations $x_i$ and frequencies $f_i$ is given by,
$\text{Average}=\frac{\sum x_i{f}_i}{\sum f_i}$

$\Rightarrow \text{Average}=\frac{393}{5}=78.6$