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  • 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.

3. 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.

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Answers (1)

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Daily pocket

allowance

Number of

children f_i

Class mark

x_i

 f_ix_i
11-13 7 12 84
13-15 6 14 84
15-17 9 16 144
17-19 13 18 234
19-21 f 20 20f
21-23 5 22 110
23-25 4 24 96
 

\sum f_i 

=44+f

  

\sum f_ix_i

=752+20f

Mean, 

\overline x = \frac{\sum f_ix_i}{\sum f_i}
\implies 18 = \frac{752+20f}{44+f}

\\ \implies 18(44+f) =( 752+20f) \\ \implies 2f = 40 \\ \implies f = 20
Therefore the missing f = 20

Posted by

HARSH KANKARIA

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