First of All Best of Luck for the D-day

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Please note that these are just my personal opinions. just choose the ones you like and filter the rest
coming to the easy bit: Quant : If you are having only 3 weeks left for exam, take other tests to see if you are still short of time in these tests. If no, i would not take
Mgmat quant tests any more. I repeat, the
Mgmat quants does not seem accurate representation of GMAT test questions.
If you are still short of time, then you may try the following:
1. divide the time into three sets : Q1-Q12 : 25 min Q12-Q25: 50min Q25-Q37: 75min It will help you track the time.
2. go back to the tests to see which section is toughest for you and which section is least time consuming.
e.g.: mixture problem, or std deviation problem... so I would see it as : I get stuck when I see 2 mixtures getting mixed or i do not know what effect range or average will make on std deviation..
unless you know the exact type of questions that you get stuck in it is difficult to improve.
If you are taking
Mgmat tests, see the report card: in which sub-section are you making most of the mistakes. that will be a good starting point.
3. Once the tough sections have been identified. go back to read the concept and solve similar problems
4. Finally, search for questions in gmatclub.com for these sections and solve them
CR: as stated in my post, see if you are able to accurately point out the conclusion, and premise of the passage. just take 25 Q of OG and mentally note the conclusion and premise then compare them with OG answers. read princeton CR once .. I some how have liking for princeton CR.
If you are not satisfied look at various online discussions. PRACTICING.. and KNOWING why an answer is wrong or right both are EQUALLY IMP.
3 WEEKS & 10 questions daily implies min 150 questions : ENOUGH to gain confidence
RC: It will consume time
some discipline to follow : 2-3min to read the passage including noting the passage framework.
Go back to the passage to confirm answers: this atleast reduced my wrong answers in RC
again a cliche: know why author is writing this topic.
Finally a quicky.... only if you are time starved in RC... read the 1st question and then start reading the passage. if you get the answer in mid of passage answer it... BUT note that if this Q is to find the purpose/aim of author it may be difficult to answer that question before reading a good chunk of the passage.
Take the Gmat prep tests if you have not taken it yet...
Hope this will help ....
cheers,
sanjeev