Most of you know why you are reading this article – to gain some knowledge, to sharpen your skills and ultimately to clear CAT and get most coveted IIM calls for admission in India’s top-notch B-schools for a colorful MBA degree. Right? But how many of you know that why do you want an MBA-degree? Your answers can be – money, lucrative job, and exotic work culture, higher growth in pay package or status symbol. Hmmm. But what after that – are there any more targets or any more goals to achieve? May be you have never thought of that.

I was asked these series of question by one of my friend in 2nd semester of my graduation from Delhi College of Engineering. My responses were in

# Important Concepts and Formulae

Hello CAT takers,

Now that we are just a few days away from CAT, you must be revising everything for one final time before CAT. Here is a compilation of all the important Concepts and formulae for Quant. Whether you need to revise the formulae or you need them while solving problems of different topics, it’s all at one place for your ready reference.

Important Concepts for CAT2018

# PRIME NUMBERS : The Most Mysterious Figures in Math

Prime numbers have always fascinated mathematicians. They appear among the integers seemingly at random, and yet not quite: there seems to be some order or pattern, just a little below the surface, just a little out of reach.
—Underwood Dudley

A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. For example, 11 is a prime number because it has no positive divisors other than 1 and 11.

# Similar Triangles

The current article deals with a frequently occurring topic in geometry in CAT- similarity of triangles. Most of you will notice that this topic is coming year after year in CAT and, as geometry questions in CAT are easy compared with other topics, mastering the concept is easier than mastering concepts in Algebra, Permutation, and Combination, or Probability.

# Divisibility Rules A. Divisibility by 2, 4, 8, 16, 32.

A number is divisible by 2, 4, 8, 16, 32,.. 2 when the number formed by the last one, two, three, four, five…n digits is divisible by 2, 4, 8, 16, 32,..2 respectively.

Example: 1246384 is divisible by 8 because the number formed by the last three digits i.e. 384 is divisible by 8. The number 89764 is divisible by 4 because the number formed by the last two digits, 64 is divisible by 4.

B. Divisibility by 3 and 9

A number is divisible by 3 or 9 when the sum of the digits of the number is divisible by 3 or 9 respectively.

# LOGARITHM

If a is a positive real number other than 1, and am = x, then we can write: m = logax, and we say that the value of log x to the base a is m.
Examples:

(i) 104 = 10000     log10 10000 = 4.

(ii) 35 = 243     log3 243 = 5.

(iii) (0.1)3 = 0.001     log (0.1) (0.001) = 3.

Properties of Logarithms

# Remainder Theorems

It is uncanny how children pick up a lot of small habits and beliefs of their parents. Even the ones that rebel against their parents bear the subconscious resemblance to their father or mother. There is a lesson for instructors in this. It is important for them to realize that students mirror their feelings about CAT. If the instructor expresses or feels that CAT is tough, or is fearful about CAT, his students will mirror the same feeling and will be less confident. If the instructor is brazen and casual about the paper and scoffs the competition, his students would reflect the same feelings. Also, it is so necessary to have unflinching faith in one’s students. I still remember that during my school days my mother used to proudly proclaim that I was an intelligent kid. I was barely scrapping passing marks in the school exams. If truth be told I was at the bottom of the class, but my mother had her blinkers on. And because of my mother, I also believed that I was second to none. It was only years later, during my boards exams, that I took to studying seriously, and managed to outperform everyone else. I don’t know if it was my mother’s blind love for me or that she could see some bright spark in me that made her claim my intelligence but it really had great effect on my attitude. And attitude, in an exam like CAT, is everything.

Well, it’s almost everything. A keen attitude towards CAT subjects’ fundamentals also plays an important role in one’s performance.

# Counting in Geometry

(a) In a plane, if there are n points of which no three are collinear, then

1. The number of straight lines that can be formed by joining them is nC2.
2. The number of triangles that can be formed by joining them is nC3.
3. The number of polygons with k sides that can be formed by joining them is nCk.

(b) In a plane, if there are n points out of which m points are collinear, then

1. The number of straight lines that can be formed by joining them is nC2mC2 + 1.
2. The number of triangles that can be formed by joining them is nC3mC3.
3. The number of polygons with k sides that can be formed by joining them is nCkmCk.

(c) The number of diagonals of an n sided polygon is nC2 – n = n × (n – 3)/2