Question

A teacher is a person whose professional activity involves planning, organizing, and conducting group activities to develop student's knowledge, skills, and attitudes as stipulated by educational programs. Teachers may work with students as a whole class, in small groups or one-to-one, inside or outside regular classrooms. In this indicator, teachers are compared by their average age and work experience measured in years. For the same in 2015, the following distribution of ages (in years) of primary school teachers in a district was collected to evaluate the teacher on the above-mentioned criterion.

The class marks of the median class of the following data is

The class-mark of the class 130-150 is:

The class marks of a frequency distribution are given as follows: 15, 20, 25, ... The class corresponding to the class mark 20 is: