What is the class mark of class 21-30 in the table of Q.3 ?
Class Interval = 21 – 30 (given)
Upper class limit = 30
Lower class limit = 21
Class marks = 1/2 [upper limit + lower limit]
Class marks = 1/2 [30 + 21]
∴ Class marks = 51/ 2 = 25.5