Final answer:
By setting up a proportion based on the percentage grade, we determined that Mia's 80% grade equates to correctly answering 100 questions out of a total of 125 questions on the test.
Step-by-step explanation:
The question asks how many questions were on a test if Mia correctly answered 100 questions and received an 80% grade. To solve this, we need to recognize that the percentage grade represents the portion of questions answered correctly out of the total number of questions.
We can set up a proportion where 80/100 (or 0.8) is equal to Mia's correct questions (100) over the total number of questions on the test (let's call this total 'x').
0.8 = 100/x
By cross multiplying, we get:
0.8 * x = 100
x = 100/0.8
x = 125
So, there were 125 questions on the test.