The marks scored by students in mathematics in a certain examination are given below: Marks scored 1 – 20 21 – 40 41 – 60 61 – 80 81 – 100 Number of students 3 8 19 18 6

3. The marks scored by students in mathematics in a certain examination are given below:

Marks scored	1 – 20	21 – 40	41 – 60	61 – 80	81 – 100
Number of students	3	8	19	18	6

Solution:

Let us make the continuous class interval.

Marks scored	Extended Class	Number of students.
1 – 20	0.5 – 20.5	3
21 – 40	20.5 – 40.5	8
41 – 60	40.5 – 60.5	19
61 – 80	60.5 – 80.5	18
81 – 100	80.5 – 100.5	6