What is the class - mark for a class 80 - 130?

The class Mark is defined as the mid-value of each class interval. It is given by:

$\begin{array}{rcl}\mathrm{Class} \mathrm{mark}& =& \frac{\mathrm{Upper} \mathrm{limit}+\mathrm{Lower} \mathrm{limit}}{2}\end{array}$

In the given class 80 - 130, upper class = 130 and lower class = 80.

Class mark$\begin{array}{rcl} & =& \frac{130+80}{2}=\frac{210}{2}\end{array}$= 105

Therefore, the class mark is 105.