Here, the maximum class frequency is 20, and the class corresponding to this frequency is 40 – 50.
So, the modal class is 40 – 50.
Now, modal class = 40 – 50, lower limit (l) of modal class = 40, class size(h) = 10
frequency (f1) of the modal class = 20
frequency (f0) of class preceding the modal class = 12
frequency (f2) of class succeeding the modal class = 11
Now, let us substitute these values in the formula