GRE Math is much easier than GMAT math. Think if you are at least competent in math you should be getting close to a perfect score after maybe 5 hours of reviewing the concepts
I think the OP is talking about the GRE math subject test…not the math portion of the GRE general test, which is what the two responders talked about. These two are completely different. The math portion of the GRE is basic high school math and is generally easier than the GMAT math as mentioned. See the description of the GRE math subject test, which includes a lot of college level math.
The GRE math subject test:
The test consists of approximately 66 multiple-choice questions drawn from courses commonly offered at the undergraduate level.
Approximately 50 percent of the questions involve calculus and its applications — subject matter that is assumed to be common to the backgrounds of almost all mathematics majors.
About 25 percent of the questions in the test are in elementary algebra, linear algebra, abstract algebra, and number theory. The remaining questions deal with other areas of mathematics currently studied by undergraduates in many institutions.