Question

the mean marks of 10 students in a class is 70 the students are divided into two groups of 6 and 4 respectively if the mean marks of the first group is 60 what will be the mean marks of the second group?

Answer 1

dear, as 70 is the mean for 10 students their total marks must be 70 x 10 = 700
First 6 with mean 60 must have 360 in total. 
So remaining marks 700 - 360 = 340 is the total for the balance 4 students
Hence their mean is 340/4 = 85