The following distribution shows the daily pocket allowance given to the children of a multistory building. Class interval: 11 - 13

Question

The following distribution shows the daily pocket allowance given to the children of a multistory building. The average pocket allowance is Rs. 18.00. Find out the missing frequency.

Class interval:	11 - 13	13 - 15	15 - 17	17 -19	19 - 21	21 - 23	23 - 25
Frequency:	7	6	9	13	....	5	4

Answer 1

Given, 

Mean = 18

Let missing frequency be V

Class interval	Mid value (xi)	fi	fixi
11 - 13	12	7	84
13 - 15	14	6	84
15 - 17	16	9	144
19 - 21	20	V	20V
21 - 23	22	5	110
23 - 25	24	4	56
		N = 44 + V	\(\sum\)fixi = 752 + 20V

Mean = \(\frac{\sum f_ix_i}{N}\)

 \(18 = \frac{752+20V}{44+V}\)

792 + 18V = 752 + 20V 

792 – 752 = 20V – 18V 

40 = 2V 

V = 20