GRE scoring

The scoring methodology for the GMAT as well as the GRE computer adaptive tests is much the same.
The CAT gives varying weights to the questions. Each CAT question is added to provide a raw score, which is converted into a scaled score. On the GRE, for example, scaled scores range from 200-800 on each of the two sections (Quantitative and Verbal). A CAT gives each correct question a different point value. The same is true for the GMAT.

The questions are divided into three roughly equal parts. The first part of the questions in any section is weighted the most. This means that the first part of the questions determines the bulk of the scaled score. The second part accounts for a lesser amount of the scaled score, and the last part counts for a relatively insignificant amount of the overall score.

All sections begin with an "average-level" question, which is scored on a scaled on a score of 500, which is an average GRE score. If one gets this question right, the scaled score could increase by almost 80 points; if one gets this question wrong, the scaled score could decrease by almost 80 points. So the first group of questions attempts to find out the range of a person's competence.

Let us take the above mentioned case for instance. If you get three questions in a row correct, your score moves to roughly 740. Then you get one wrong. Assuming this would be a more difficult question, your score remains at 740 and you are given a question of difficulty level corresponding to 740. Getting this wrong will get you a question of difficulty level corresponding to 660 .Getting this right will now point to your score range between 660 and 740.
The questions that follow will now range between the given scores so to zero down exactly on your competence level score.

In short, along with getting a question right or wrong, the level of difficulty of the next question will change. A correct answer "rewards" you with a harder question; an incorrect answer "rewards" you with an easier question. . There are a significant number of experimental questions sprinkled in as well, and the experimental questions do not factor into your score.

You are required to answer all Questions. You will be penalized for leaving questions unanswered.
Be cautious. You want to be sure about accuracy on early questions, and worry less about getting to the last questions in a section. Remember, later questions have a progressively smaller impact on your overall score, but you need to answer all of them. If you are pressed for time, guess. The most important piece of advice is that you should not leave any questions unanswered.