Question

If 150 is a mean of 200 observation and 100 is the mean of some 300 other observation find the mean of the combination.

Answer 1

Mean = total no. / total observation.
Mean = total no. / 200.
150 = total no. / 200
Total no . = 150× 200 = 30000..........(1).
Mean = total no. / total observations.
100 = total no. / 300
Total no. = 100 × 300 = 30000..........(2)
Add : equation 1 and 2
30000 + 30000 = 60000
Mean = total no. / total observations
Mean = 60000/500 = 120 .
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Answer 2

N.O.T = No. of terms

S.O.T = Sum of terms

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