Yes. 6 months are definitely enough to prepare and crack the CAT provided you are ready to put in the required efforts. As a matter of fact, most of the aspirants pace up their preparation efforts in the last 6 months.CAT is an aptitude test and the syllabus of CAT is not so vast. It only needs a lot of practice. So first of all go for the complete analysis of syllabus. CAT consists of 3 sections - Verbal Ability (VA), Logical Reasoning and Data Interpretation (LR & DI) and Quantitative Ability (QA). Linearly taking you have about 2 months to prepare for each section, which in my opinion is more than enough. Now, all you need to follow a systematic approach towards preparation.