I suggest you check the following website , helps a lot in understanding how go do question quickly.
1. Also do GMAT CLUB MATHS book
1) GMATCLUB Quizzes. One can start with 500 level questions initially and move to middle level and subsequently highest level.
2) Jeff sackmann's challenge sets. Soembody who is already scoring around 40 in quant won't require the basic one. The eight challenge sets are divided topic wise and they have mostly 600-700 level questions.So after the end of each topic, for eg geometry, one can make sets of 20-30 questions and do them timed using a timer.
3) For GMAT, the best resource is gmatclub, check out these links again the questions are level and category wise, exactly what we need.
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