Alphametics The Art of Numbers

As CAT 2018 preparation starts heating up, I am going to flag the race with an oddball topic: Alphametics. What are alphametics or cryptarithms as they are also known?

Alphametics are number puzzles in basic arithmetic operations where digits are represented by alphabets. It is customary that different digits are represented by different alphabets. Why are alphametics relevant? Because they require a good knowledge of the properties of numbers and skill in working with them. Solving alphametics helps you quickly identify the solution to many problems which might otherwise require a good amount of time.

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Similar Triangles

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.

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 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.

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Remainder Theorems

Remainders-CAT-MAT-GMAT

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.

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Last two digit
Last two digits

I am dividing this method into four parts and we will discuss each part one by one:

a. Last two digits of numbers which end in one
b. Last two digits of numbers which end in 3, 7 and 9
c. Last two digits of numbers which end in 2
d. Last two digits of numbers which end in 4, 6 and 8

Before we start, let me mention binomial theorem in brief as we will need it for our calculations.

Last two digit
Binomial theorem

Last two digits of numbers ending in 1

Let’s start with an example.

What are the last two digits of 31786?

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last non zero digit

At every step in life, we face diverse problems. They may be related to our family, health, education, career and much more. There can be no one who says that I never had a problem. Srimad Bhagwatam [10.14.58] says ‘padam padam yad vipadam’ which means that at every step in life we face problems. Now how to eradicate our problems is the biggest problem. One thing is sure that we cannot escape the discomfort created because of the problems of life. So the wiser advice will be to find out the root cause of our problems and try to kill it. And remember, we must help each other by solving each other’s problems. That makes life smoother. You get dependable and caring friends which you’d like to carry along throughout life.

Coming back to our math worries, many students have repeatedly asked us to create a Quant corner where we can post our (beautiful) solutions to beautiful math problems and discuss some small concepts. So here we are! This place is open for discussions as that is the best way of learning. So let’s start today’s mathematical extravaganza.

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Grammar

  1. A NUMBER VS THE NUMBER

As a stand-alone word and as a collective noun, “number” can take a singular or a plural form.

e.g. Two hundred persons were at the party; the number(s) is (are) just astounding.

However, when preceded by an article and followed by the preposition “of”, “number” is singular and the verb that follows “number” will be conjugated singular or plural depending on whether there is a definite or indefinite article in front. The expression ‘the number of . . .’ is singular, while ‘a number of . . .’ is plural.

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