if I have got 80.0% percentile in AIIMS ??? then how many questions are right ??

Percentile scores are the scores based on the relative performance of all those who appear for the AIIMS examination. Basically the marks obtained are transformed into a scale ranging from 100 to 0 for each group (shift) of examinees.
The Percentile Score indicates the percentage of candidates that have scored EQUAL TO OR BELOW (same or lower raw scores) that particular Percentile in that examination. Therefore the topper (highest score) of each group (shift) will get the same Percentile of 100 which is desirable. The marks obtained in between the highest and lowest scores are also converted to appropriate Percentiles.
The Percentile score is the Normalized Score for this examination.

So this is quite difficult to provide the number as the percentile depends on above said criteria.

Hope this helps!!!

Good Luck!!!