Ms. Smith gave a math unit test to each of her three classes. Each class has the same number of student. Ms. Smith grades 75% of test, which is 15 papers. How many student does she have in each class?
Since Ms. Smith grades 75% of the test, which is 15 papers, we can calculate the total number of students in each class by setting up a proportion.
Let x be the total number of students in each class.
75% of x is equal to 15 papers, so we can set up the following equation:
0.75x = 15
Solving for x:
x = 15 / 0.75
x = 20
Therefore, Ms. Smith has 20 students in each of her three classes.