Mrs. Smith gave a math unit test to all her classes. Mrs. Smith grades 75% of the test, which is 15 papers. How many students does she have in her classes?

Answer 1

To find the total number of students in Mrs. Smith's classes, we can use the information provided about the percentage of the tests she grades and the number of tests she graded.

Let \( x \) be the total number of students in Mrs. Smith's classes. According to the problem, Mrs. Smith grades 75% of the tests:

\[ 0.75x = 15 \]

Now, we can solve for \( x \) by dividing both sides by 0.75:

\[ x = \frac{15}{0.75} \]

To perform the division:

\[ x = 15 \div 0.75 = 15 \times \frac{100}{75} = 15 \times \frac{4}{3} = 20 \]

Thus, the total number of students in Mrs. Smith's classes is \( \boxed{20} \).