Did I Get This Simple Math Average Problem Right?

Question

Hi! I need to find students to fill a classroom with. There are 2 classes that I need to fill 50% of each class and 7 classes that I need to fill 33.3% of each class. Overall, what is the average percentage I need to contribute between all the classes combined? What am I expected to contribute overall? I thought this equation might be the best way to solve it.

                                                           (50% X 2) + (33.3% X 7) / 9= 37%

Is that formula the correct formula to solve the problem? Is 37% the right answer? Thank you!

Answer 1

The calculation is correct but your weighted average formula needs parentheses around the numerator. You are assuming that all the classes are the same size (let's say S). So your answer is that you are averaging contributing .37S to each class and 9 x .37S actual students. You have to know S to be able to give a number.