The following distribution shows the daily pocket allowance of children of a locality. The mean pocket allowance is Rs. 18. Find the missing frequency $f$.

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

"

Given:

The given distribution shows the daily pocket allowance given to the children of a multistorey building.

The average pocket allowance is Rs 18.00.

To do:

We have to find out the missing frequency.

Solution:

Mean $=Rs.\ 18.00$

Let the missing frequency be $p$.

 We know that,

Mean $=\frac{\sum{f_ix_i}}{\sum{f_i}}$    

Therefore,  

Mean $18=\frac{752+20p}{44+p}$

$18(44+p)=752+20p$                  

$792+18p=752+20p$

$792-752=20p-18p$

$p=\frac{40}{2}$

$p=20$

The missing frequency is $20$. 

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Updated on: 10-Oct-2022

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