Class `(1)`	Frequency `(f)` `(2)`	Mid value `(x)` `(3)`	`d=(x-A)/h=(x-45)/10` `A=45,h=10` `(4)`	`f*d` `(5)=(2)xx(4)`	`cf` `(7)`
0 - 10	4	5	-4	-16	4
10 - 20	2	15	-3	-6	6
20 - 30	18	25	-2	-36	24
30 - 40	22	35	-1	-22	46
40 - 50	21	45=A	0	0	67
50 - 60	19	55	1	19	86
60 - 70	10	65	2	20	96
70 - 80	3	75	3	9	99
80 - 90	1	85	4	4	100
---	---	---	---	---	---
	`n = 100`	-----	-----	`sum f*d=-28`	-----

Mean `bar x = A + (sum fd)/n * h`

`=45 + (-28)/100 * 10`

`=45 + (-0.28) * 10`

`=45 -2.8`

`=42.2`

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To find Median Class
= value of `(n/2)^(th)` observation

= value of `(100/2)^(th)` observation

= value of `50^(th)` observation

From the column of cumulative frequency `cf`, we find that the `50^(th)` observation lies in the class `40 - 50`.

`:.` The median class is `40 - 50`.

Now,
`:. L = `lower boundary point of median class `=40`

`:. n = `Total frequency `=100`

`:. cf = `Cumulative frequency of the class preceding the median class `=46`

`:. f = `Frequency of the median class `=21`

`:. c = `class length of median class `=10`

Median `M = L + (n/2 - cf)/f * c`

`=40 + (50 - 46)/21 * 10`

`=40 + (4)/21 * 10`

`=40 + 1.9048`

`=41.9048`

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