Answer:
80 questions
Step-by-step explanation:
Given that a student received an 85% grade on his test, and that he got 12 questions wrong:
We could infer that if he answered all of the test questions correctly, then he would have received a perfect score of 100% on his test.
Since he got 12 questions wrong, then it means that those wrong answers account for the 15% out of receiving a 100% grade on his test (or: 100% - 85% = 15%).
Let x = number of test questions
In order to find how many questions were on his test:
12 questions = 15% (or 0.15) of the total number of questions (x)
12 questions = 0.15x
Divide both sides by 0.15 to isolate x:
[tex]\displaystyle\mathsf{\frac{12\:questions}{0.15}\:=\:\frac{0.15x}{0.15}}[/tex]
x = 80 questions
Therefore, there were 80 questions on his test.
