Q. 183.8( 17 Votes )

The mean of the f

Answer :


Given, Sum of frequency = 50


5+ f1 + 10 + f2 + 7 + 8 = 50


f1 + f2 = 50 – 5 – 10 – 7 – 8


f1 + f2 = 20


3f1 + 3f2 = 60 (i) [Multiply by 3]


And mean = 62.8


= 62.8


= 62.8


30f1 + 70f2 = 3140 – 2060


30f1 + 70f2 = 1080


3f1 + 7f2 = 108 (ii) [Divide by 10]


Subtract (i) from (ii), we get


3f1 + 7f2 – 3f1 – 3f2 = 108 – 60


4f2 = 48


f2 = 12


Put value of f2 in (i), we get


3f1 + 3 * 12 = 60


3f1 + 36 = 60


3f1 = 24


f1 = 8


So, f1 = 8 and f2 = 12


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