A student answered of the questions in an exam correctly and answered 10 questions wrong. What was the total number of questions in the exam?
Assume that the student answered all of the questions. If of the questions were answered correctly, must have been answered incorrectly. We are told that 10 questions were answered wrong, so
We need to double to get .
Total number of questions questions.
Therefore, there was a total of 20 questions in the exam.