Hi ashokv1990,
Since you posted this in another Forum on this site, I've pasted over my response from there:
A 640 is a strong initial CAT Score. Assuming that you took the FULL CAT and did so in a realistic way, then you you're in a good position to hit your score goal. Many Test Takers spend 3 months (or more) before they hit their 'peak' scores though, so you might need more study time than you've allotted.
While studying, you should plan to take FULL-LENGTH CATs (including the Essay and IR sections) at regular intervals (1 FULL CAT every 1-2 weeks); your current plan does not appear to include those CATs.
1) What were your Quant and Verbal Scaled Scores on this CAT?
2) What is your exact Official Test Date?
3) When are you planning to apply to Business School?
4) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich