The mean number of students in a classroom at school A is 32.5 and there are 25 classrooms. The mean number of students at school B is 29.6 in 12 classrooms. At school C the mean in each class is 15.3 for 10 classrooms. What is the mean number of students per classroom for all the schools combined?
A) 1320.7
B) 28.1
C) 25.7
D) 28.7

Question

Quizplus · Accepted Answer

To find the overall mean number of students per classroom, we need to find the total number of students and divide by the total number of classrooms. 
For school A, there are 25 classrooms with a mean of 32.5 students per classroom, so the total number of students is 25 x 32.5 = 812.5
For school B, there are 12 classrooms with a mean of 29.6 students per classroom, so the total number of students is 12 x 29.6 = 355.2
For school C, there are 10 classrooms with a mean of 15.3 students per classroom, so the total number of students is 10 x 15.3 = 153
The total number of classrooms is 25 + 12 + 10 = 47
The total number of students is 812.5 + 355.2 + 153 = 1320.7
The mean number of students per classroom for all the schools combined is 1320.7 / 47 = 28.1, which is closest to choice B.

The Mean Number of Students in a Classroom at School