The mean of marks secured by 60 students in division A of class X is 66, 45 students of division B is 62 and that of 75 students of division C is 60. Find the mean of marks of the students of three divisions of Class X.
1). 61.8
2). 62.5
3). 61.1
4). 63.9
Total marks of division A = 60 × 66 = 3960
Total marks of division B = 45 × 62 = 2790
Total marks of division C = 75 × 60 = 4500
Total marks of all students = 3960 + 2790 + 4500 = 11250
Total number of students = 60 + 45 + 75 = 180
Average marks = 11250/180 = 62.5