The mean score of 25 observations is 80 and the mean score of another 55 observations is 60. Determine the mean score of the whole set of observations.

Given,


Mean score of 25 observations = 80


Total score of 25 observations = 25 × 80 = 2000.


Mean score of another 55 observations = 60


Total score of 55 observations = 55 × 60 = 3300.


Total observations = 55 × 25 = 80


Mean score of whole set of observations =



Hence, Mean score of whole set is 66.25.


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