We have given three school there, School A, School B and School C.
We are going to use following formula.
Total number of student in a school = Mean of number of student × Number of classrooms.
School A
Mean of students in School A = 32.5.
Number of classroom in School A = 25.
Number of students in School A = Mean × number of classrooms = 32.5×25 = 812.5
School B
Mean of students in School B = 29.6.
Number of classroom in School B = 12.
Number of students in School B = Mean × number of classrooms = 29.6×12 = 355.2
School C
Mean of students in School C = 15.3.
Number of classroom in School C = 10.
Number of students in School C = Mean × number of classrooms = 15.3×10 = 153.
Total sum of number of classes in all schools = 25+12+10 = 47.
Total sum of all students in all schools = 812.5 +355.2 +153 = 1320.7 .
The mean number of students per classroom for all the schools combined =
= = 28.1
The mean number of students per classroom for all the schools combined= 28.1