I want to suggest some strategies to crack Quant.
What is tested?The level of Math-skills required is of High-school level.
All the stuff tested here is on "the basics". One should be thorough in basic formulae and concepts to crack the Quantitative section of GMAT.
Time-Strategy:Time may not be a big constraint while solving the 'Quantitative' section.
For Quantitative section, the given 75 minutes to solve 37 Q's leaves us a solid 2 minutes (or 120 seconds) time for each Q'. But as a PS problem generally takes lesser time than a DS one takes, there is no strict emphasis on limiting each problem to 2 minutes. One problem may take 150 seconds while the other may take 90 seconds only. So instead of keeping track on time taken for each problem, it is better to have an overall track on a bunch of problems (say 5 or 10 at a time). Keeping this in mind while practicing problems builds one's confidence in tackling any issues with time.
"Calculations performed in mind save a lot of time when compared to calculations put on paper"
Silly Mistakes:Don't be too fast while solving the problems. Even if you are strong in Quant section, go with a balanced approach. Be careful with the traps. More balance is required especially in dealing with DS problems as we are more prone to traps there.
After completing OG material,try out some advanced Quant books like Manhattan etc., to get more varieties of flavour. Go through the challenge Q's, 700-800 level Q's on prominent sites and materials.
DS-Strategy:DS Q' is a bit difficult in the sense that it requires a bit more time to solve when copmapred to a PS Q'. It requires a careful approach which deals a step by step elimination of the options.If one does not follow the process, there is a high chance of landing on a wrong choice.Weigh the two given statements independently to decide whether either one alone is enough to answer. If both the statements are not independently enough to solve the problem, then check whether both the statements together can do.
At this level, you might be knowing much of this stuff. But I thought summing up these points at one place might help to some extent if not much.
All the best.
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Ravi Sankar Vemuri