GMAT Preparation

Hi,
Unfortunately, the answer to this question is "YES". CAT preparation won't be sufficient enough for GMAT and the same holds true if you are preparing for GMAT. This is because the intention to check on the areas are very different in both the exams. CAT tests your ability mainly on your 1- Quantitative abilities 2- Data Interpretation/ Logical Reasoning and 3- Verbal Ability. GMAT on the other side tests your, quant, Verbal, AWA, IR. You may think Quant and Verbal overlap in both but this isn't enough as the difficulty is not the same in both. Quant in CAT is at a higher level than GMAT. Similarly Verbal scores point in GMAT over quant. Thus perpetration for one exam doesn't assure you are ready for other. My suggestion would be to focus on one exam according to the colleges you want to go for and your final future plans.
Thanks.

Start early and by August, shortlist 8-12 universities that you will apply to. Visit university websites and note application requirements, deadlines etc. By September, be familiar with bank loan options and scholarships to fund your studies. Begin by downloading admissions brochures from the university websites. Most brochures are out more than a year earlier. Do some initial research on various accommodation options. Crack the exams: June 2016 to December 2016. Prepare for required standardized tests like GMAT GRE SAT TOEFL or IELTS depending on the course and university. By June-July or three months before the test date, register for GMAT/ GRE. Register for TOEFL/IELTS at least a month before the test date. Take the required tests around September. Plan for buffer time in case you need to retake the test. Check test taking and re-exam process and guidelines. Its application time: August 2016 to October 2016. Shortlist the colleges and prepare for your application. Think hard about what makes you unique as an applicant and sketch out your strengths and self assessment. Contact your professors and direct managers for the required 2-3 reference letters. At least a month before your application deadline. Check the deadline timetable! Begin drafting your SOP and essays. Give a months time to structure these documents properly. Apply before the deadline!
What next: November 2016 to April 2017
Don't delay replying to college e-mails. And there will be quite a few! Appear for personal/video interviews. These are scheduled around January to March. Once you get acceptance letters, make your decision as soon as possible. Depending on the deadline, notify the universities of your decision. You will need to pay a non-refundable deposit to confirm your admission. Visa and money matters: May 2017 to July 2017. Search for and begin applying for external scholarships (if applicable). Apply for student loan, after you get your acceptance letter. Gather paperwork for your student visa. Check visa requirements. Apply for student visa in time. Keep in mind the time taken for visa processing!
Get ready to fly: July 2017 to August 2017
Book airline tickets. Arrange for an International Debit/Credit card. Collect all the documents and their photocopies, to take along. Check out Pre-departure checklist!

First of all, both CAT and GMAT have different patterns. Although, both measure a person's abilities like Quantitative and verbal, but the content differs. GMAT is an adaptive test, which means as you answer the question right, a harder question will be given to you and if you answer wrong, a question easier or equal to your last question will be given. You can move forward only if you answer the current question. Whereas, CAT is a linear test where questions are numbered and you can go back and forth anytime and choose which question you want to answer first. The verbal ability parts of both the exams are somewhat different. While GMAT has Sentence Correction, Reading Comprehensions and Critical Reasoning. CAT has some similar question types but it focuses more on grammar and vocabulary. GMAT also has Analytical Writing Assessment and Integrated Reasoning which is different from Logical Reasoning and Data Interpretation questions in CAT. So Preparing for CAT may somewhat help, but since the pattern differs you have to study according to the question type and timing of the exam. Again, GMAT requires SMART studying whereas CAT requires a lot of practice.