SOLUTION: from the following data find the missing frequency when mean is 15.38. ___________ ___________ ___________ ___________ ______ MARKS: 10 12 14 16 18

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Question 717065: from the following data find the missing frequency when mean is 15.38.
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MARKS: 10 12 14 16 18 20
FREQUENCY: 3 7 12 20 ? 5
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Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
If "n" is the missing frequency then:

Simplifying...
%2830%2B84%2B168%2B320%2B18n%2B100%29%2F%2847%2Bn%29+=+15.38
%28702%2B18n%29%2F%2847%2Bn%29+=+15.38
Eliminate the fraction by multiplying each side by (47+n):
702%2B18n+=+%2847%2Bn%29%2A15.38
702%2B18n+=+722.86+%2B+15.38n
Subtracting 15.38n:
702%2B2.62n+=+722.86
Subtracting 702:
2.62n+=+20.86
Dividing by 2.62:
n+=+7.9618320610687022900763358778626

Since "n" was a frequency, it should be a whole number. The reason we did not get a whole number for n must be either
  • We made a mistake. Check the work to see if we did. Or...
  • The average we were given is a rounded-off number. In this case, "n" must be 8.