CDS is a national level entrance examination conducted by UPSC twice a year. CDS exam is scheduled to be conducted on February 5, 2017. The main objective of this exam is to select candidates for recruitment in Indian Defence forces. Mathematics ection is a key factor in CDS to ensure good score in the exam. The mathematics paper consists of 120 questions in UPSC CDS. The duration of the examination is 120 minutes.
Number system is one of the most important topics of elementary mathematics. It helps in boosting overall score of the candidate. This section contains approximately 15% of weightage in CDS exam. Number system is the fundamental section of any topic in mathematics. Here, the paper pattern for number system in elementary mathematics section.
|Topics||No. of questions|
|Basic of number system||4|
|LCM & HCF||3|
|Surds & Indices||2|
Candidates need to focus on the questions of every topic. Here, we are providing concepts and methods for each topic. Candidates can follow these concepts to score better in number system questions.
Basics of number system
Candidates must be good in calculations, counting, analysis etc. They need to solve these questions in less time by shortcut tricks. For example:
Q: 1397*1397 =?
= 1951609; By formulae (a2-2ab+b2)
LCM & HCF
These questions need only some practice to solve in single attempt. Candidate need to focus on particular type questions in HCF & LCM. Here is the example of that type of question which are asked in CDS exam:
Q: The H.C.F. of two numbers is 23 and the other two factors of their L.C.M. are 13 and 14. The larger of the two numbers is:
Ans: Clearly, the numbers are (23*13) and (23*14)
Therefore, the larger number = 23*14 = 322
Surds and Indices
These questions look complicated and tricky but candidates can solve it in few seconds by an easy method. For example:
Q: If 5a = 3125, then the value of 5(a-3) is:
Ans: 5a = 3125,
5a = 55,
therefore, 5(a-3)= 5(5-3)= 52=25
In these questions, the method is depending upon simple arithmetic rules. It needs to only give clear attention for a while. For example:
Q: (6 + 4) *5
Ans: first solve the numbers inside the bracket 6 + 4 = 10, then 10*5 = 50.
This is the simplest question of mathematics in CDS exam. It gives bonus marks in elementary, e.g.,
Q: Find the prime factors of 102.
Ans: The prime factors of 102 are 2, 3 and 17.
There are some important tips to solve number system questions in CDS 2018. Candidates can go through following points that will help in their preparation strategy:
*The article might have information for the previous academic years, please refer the official website of the exam.