Question

A student answers 80% of the questions on a math exam correctly. If she answers 20 questions correctly, how many questions are on the exam?

Answer 1

If 80% of the questions represent 20 questions, we can use the following rule of three to find how many questions are 100% of the questions:

`\begin{gathered} \text{percentage}\to\text{questions} \\ 80\text{\%}\to20 \\ 100\text{\%}\to x \end{gathered}`

Now we can write the following equation and solve it for x:

`\begin{gathered} (80)/(100)=(20)/(x) \\ 80\cdot x=20\cdot100 \\ x=(20\cdot100)/(80) \\ x=25 \end{gathered}`

Therefore the exam has 25 questions.