In CAT, one of the major topics in Quantitative section is Number Systems. This topic can have a weight of as much as 10% in that section. This 10% can make a difference of 5 percentile in one’s CAT percentile. So, it is quite important for a serious aspirant to be thorough in all the concepts in this topic that are possible to appear in CAT. Students should spend considerable amount of time on practising different varieties of problems rather than on reading theory.
Sub-topics that students have to cover:
- Prime number classification
- Factors and Divisibility rules
- Number of zeroes and last non-zero digit in a factorial
- Unit digit, last 2 digits and last 3 digits of Np
- Remainders
- Base System
- HCF and LCM
As most of these sub-topics are interrelated, it is important to prepare in an orderly fashion (as mentioned above), so that the topics that are covered initially must act as a base for the remaining topics. Suppose, if a question asks to find the remainder of 77193 when divided by 89, one has to use the Euler’s theorem that deals with co-prime numbers, which is covered in the topic of Prime Number classification. So, it is recommended that students make a plan of the order in which the sub-topics are covered, before starting off their preparation in any main topic.
What strategy should an aspirant follow while preparing Number Systems?
Speed and Accuracy of the candidate are the two main aspects that are tested extensively in CAT. Number systems have quite a number of formulae that can help in solving the questions quickly, which would otherwise take a lot of time to solve. While preparing, students should maintain a cheat-sheet (formula sheet) so that it gets easier for reference when needed. Take a look at the cheat-sheet prepared by the Cracku here . Accuracy in this topic is directly proportional to the amount of practice (not the reading part but the solving part) done by the student. So, with a good amount of practice and making proper use of the formulae, one should be comfortable in dealing with questions in this topic with ease. As this topic deals with numbers, it is highly recommended that students make good use of the calculator (introduced this year) that is provided in CAT 2015, if needed.
It is recommended that a candidate analyses all the questions after taking a mock test and checks for alternate approaches, which might help in solving the question faster. Any new formula that one comes across with is to be noted in the cheat-sheet. A serious aspirant should solve the questions that were incorrectly answered again in order to remember the mistakes he made. Not making the same mistakes again is the key to success in any competitive exam.
Number-Systems Cheat-Sheet: https://cracku.in/cat/quant-and-di/number-systems/cheatsheet
Free Mocks: https://cracku.in/cat/mockcat
Previous CAT papers: https://cracku.in/cat/previous-cat
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