One advantage of allowing math students access to a workbook answer key is that it enables them to verify whether they are working the problems correctly. If the answer key also features step-by-step solutions to each problem, students can use it as a study guide when preparing for exams.
Without access to the correct answer upon finishing a math problem, the student has no guaranteed way to know she approached solving the problem correctly. If the answer is available to her, she knows if she needs to go back and try to work the problem again or request help from her teacher.
Although some math students may use an answer key to cheat on their homework, doing so only hurts them when they are unable to work problems on their own come test day. Teachers can protect against students cheating by requiring them to write out all of the steps they used to solve each problem. Another option is to provide a key with answers to select problems instead of all of them.
Some answer keys provide explanations of how to solve the problems in the workbook. This type of key is a useful study tool when students use it appropriately, because it helps them see where they are going wrong when they get stuck on assignments.