Don't. GMAT is a computer adaptive test, which means that the level of questions is not uniform, but depends upon your performance in the test (section) up till that question. Therefore, if you are performing well on the test, you can expect tougher questions (and hence tougher passages). If you set a deadline of 3 minutes for completing the entire RC, you'll be prone to making more errors.

READING SPEED
If you mean reading the passage in 3 minutes, that is a good, reasonable target to set for a medium length passage. If your test is more than 2 months away, start off reading books to improve your reading speed. You should be able to read (and process) text from a simple novel in 75% of the time you expect to take on the GMAT. That is, if you have a target of 3 minutes, you should be able to read and understand a paragraph from a relatively easy novel within 2 minutes and 15 seconds.

If you are a reading beginner, start off with simple novels by Indian writers. If you are a novice, try harder novels, newspaper articles or maybe a few research papers.

INFORMATION PROCESSING
Coming to how you process the information while reading the passage, compartmentalize the information. Identify the main idea of the passage (this is generally in the first two or three sentences). Follow the logical path, and also recognize the tone of the author (this comes with time, as you practice more and more passages).

Finally, practice, practice and practice! Solve all the OG questions before your exam. Pace yourself when solving these questions. Remember, your goal is NOT to finish at the earliest, but to finish in time.

For any other queries or for tutoring, feel free to reach out.

Saravan V
GMAT: 750
CAT: 99.94%ile