The mean of 20 observations is 7 if each observation is multiple by 3 and then 5is added to it then the mean of the new data set is

 

 

 

 We know,

       Sum of observations/ no of observations =mean

        Given,

      No of observations=20 and mean is 7

   So, sum of observations =140

   If      Each observation is multiplied with 3  and then 5 is added then , sum of observations=425

         No of observations =21 then mean=20.2

the mean of a set 10 observation is 4 another set of 20 observation is added to it which makes the mean of the combined set equal to 6.the mean of second set is