Why do math problems require you to show your work?

Teachers often require students to show their work on math problems to ensure students used the proscribed method of solving the problem, ensuring the student has learned the material appropriately. Showing work also makes it more difficult for students to simply copy answers from one another.

Showing the work done to arrive at an answer also makes it easier for the teacher to see where a student who did not get the correct answer made the mistake, thus making it easier to explain to the student what he did incorrectly. For students who got some of the process correct but made mistakes, teachers may decide to provide partial credit for partial understanding.