Ms. Quarles gave the same math unit test all of her classes. She grades 25% of the tests, which is 30 papers. How many students does Ms. Quarles have in total?
If 30 papers represent 25% of the total number of students, then we can set up the following proportion:
30/0.25 = x/1
Solving for x, we get:
x = 30 / 0.25
x = 120
Therefore, Ms. Quarles has 120 students in total.