Question

The aversge of the marks obtained in an examination by 8 students was 51 and by 9 other students was 68 the average marks of all 17 students was

Answer 1

 x1 + x2 + ... + x8   = 51  and   x9 + x10 + ... +x17    = 68
             8                                                9
 x1 + x2 + ... + x9 + .. + x17    =  (51*8) + (68*9)   = 60
                  17                                        17