Krishna
0

Step 1: Recall the formula of the mean of the grouped data


          NOTE: The mean (or average) of observations is the sum of the values of

                      all the observations divided by the total number of observations.


                  Let x_1, x_2, x_3............, x_n be observations with respective

                      frequencies f_1, f_2,............f_n


                          Mean = \frac{f_1x_1 + f_2x_2 + ........f_nx_n}{f_1 + f_2 +..........+ f_n}


                                          or


                                Mean = \frac{\Sigma f_ix_i}{\Sigma f_i} 


Step 2: Re-organize given data in the table and find the sum of all observations.


                

    

              Sum of the values of all the observations   \Sigma f_ix_i = 1390


              Total number of observations \Sigma f_i = 35


                      So, the mean = \frac{1390}{35}


                        Mean = 39.71