Regardless of the subject and your confidence in the things that you have learned, without revision, you cannot guarantee that you will remember everything at the time of the exam. For any student who has appeared for mock tests or solved previous year question papers, he or she must have realized that many times, there are instances where one knows what is to be done, but is not sure how it is to be done. Especially for subjects like Maths where a little change of operation like plus changing to a minus or a division changing to multiplication or anything like that, can lead to you solving the entire problem on a completely opposite tangent. The only way you can ensure this does not happen to you is by doing thorough revision at regular intervals. It is, therefore, safe to say that revision is essential for getting a good score and good and sufficient revision can easily boost your score by up to 5 to 10%.