Question

In a frequency distribution, the mid point of a class - interval is 20 and width of class is 8. Find lower limit of d class interval

Answer 1

lower limit = class interval - width/2
= 20- 4
= 16

Answer 2

[lower limit + upper limit] /2 = 20
so   lower limit + upper limit = 40

       upper limit - lower limit = 8

Subtract the 2nd equation from the 1st:  
       2 * lower limit = 32

      lower limit of the class = 16.