Question

when mid value is givn how to find class interval

Answer 1

by difference between mid class , class interval could be found

Answer 2

U can solve it by first multiplying the given mid-values by 2.
For eg:- After multiplying, u get:-
10,20,30,40,50,60,70 and so on......
Then class intervals would be :-
10 - 20, 20-30, 30-40, 40-50, 50-60 and so on........
I hope this helps u......