9. If the mean of the distribution is 57.6 and the sum of its observations is 50, find the missing 

frequencies f1
and f2
C.I-
0-20 20-40 40-60 60-80 80-100 100-120
Fi
7      f1       12        f2        8          5

We have the following data

Class

Frequency

fi

Mid-values

xi

 f ixi
0-20710 70
20-40f 130 30f 1
40-601250 600
60-80f 270 70f 2
80-100890 720
100-1205110 550

 

Since,

Again,

Multiply equation 1 by 3 and subtract it from equation 2 to get,

 

 

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