Question

formula of step deviation methord of mean

Answer 1

A+summation of fiui/summation ui*h

Answer 2

HULLOA friend!!
Rajdeep here....

Let CI be the Class Interval.
First of all, you need to find Class Mark, which we call "$x$", which is found by adding the upper class interval and lower class interval and then dividing it by 2.

Add all the given frequencies. Take the middle term of class mark (i.e., the number which is present in the middle of $x$ (Class mark) as the Assumed mean (A).

d = $x$ - A 
Now, take "i" as the difference of the upper class interval and lower class interval. Generally, it is 10.

Find U = d/2
That is, divide each values of d (x-A) by 2 and you will get values of U.
Find each products of frequency and U (fU). Add them up. Let the sum be S. Also, let the sum of the frequencies be T.

Hence, mean =
$A + \frac{S}{T} x i$


Thanks!!