If the median of the following frequency distribution is 32.5, find the values of f1 and f2.

Class	Frequency
0 - 10	f1
10 - 20	5
20 - 30	9
30 - 40	12
40 - 50	f2
50 - 60	3
60 - 70	2
70 - 80	40

Sum of the Frequencies
f1 + 5 + 9 + 12 + f2 + 3 + 2 = 31 + f1 + f2
But N = 40
⇒ 31 + f1 + f2 = 40
⇒ f1 + f2 = 9
⇒ f2 = 9 - f1
Given median is 32.5 which lies in class 30-40
So median class is 30-40
Median = l + h/f[N/2 - C]
Here l = 30, N/2 = 20, h = 10, f = 12, C = f1 + 14
⇒ 30 + 10/12[20 - (f1 + 14)] = 32.5
⇒ 6 - f1 = 3
⇒ f1 = 3
f2 = 9 - 3 = 6