The percentiles vary slightly from year to year depending on the test takers. For instance, 750 used to be 99th percentile, but now you have to get 760 to get 99th percentile. However, an approximate conversion chart is published in most test prep books. Out books have the chart in the front of our arguments book.

I know for sure that the overall percentile is not an average of the two percentiles. For instance, I have seen 83 percentile math 99 percentile verbal scale to 99 percentile overall. The chart is your decoder ring; I would be surprised if your materials don't have it.

On a seperate but related note, different raw scores can calculate to the same final score. There's a good thread about it here: https://www.urch.com/forums/gmat/17371-h ... cores.html

Best wishes,

Tatiana