the class marks of distribution are

47,52,57,62,67,72,77,82  determine the class size,class limit,ture class limits.

1. Class size = Difference between class marks of two consecutive classes.
        =52 - 47 = 5

2. Lower-class limit = class marks - 1/2 of class size
 Upper class limit = class marks + 1/2 of class size
  Therefore,
  for class mark 47 ,class-limits are: 47-2.5 and 47+2.5
 = 44.5 and 49.5
 =44.5 - 49.5
  for class mark 52, class-limits are: 52-2.5 and 52+2.5
 =49.5 - 54.5 
  Similarly, you can calculate the class limits for other class marks.

3. Since, the class-limits form a continuous frequency distribution; the true class limits and the class-limits are the same.