The Mechanical Comprehension section of the exam tests your knowledge of machines and how they work. You will need to be familiar with diagrams because you will be answering questions about them. This section also requires you to have math skills in order to do well. You may be asked to explain mechanical functions using mathematical formulas. If you are taking a computer-based exam, you will be required to answer 16 questions. Paper and pencil exams require you to answer 25 questions. It’s important to note that the Mechanical Comprehension subtest is not a part of your AFQT score. Instead, the score you get on this subtest helps determine whether you are eligible for certain military jobs. Failing this section of your exam does not disqualify you from enlisting in the army as long as you get a passing AFQT score.