The overall percentage of increase of students for this middle school is about 17.2%
To do this you have to know the number of students in each grade and add them together and do this:
390 x 0.1 = 39 Students
350 x 0.22 = 77 students
420 x 0.2 = 84 students
Add all the number of students and do this:
(200 students over 1,160) x 100%
(Increased students over original students) x 100%
0.172 x 100% = 17.2%
The percentage increase of the students of the middle school is about 17.2%
