**Last Updated on Sep 18, 2019**

### What is Number System?

A number system is a system of writing for expressing numbers. It is the mathematical notation for representing numbers of a given set by using digits or other symbols in a consistent manner. It provides a unique representation of every number and represents the arithmetic and algebraic structure of the figures. It also allows us to operate arithmetic operations like addition, subtraction, and division.

#### Types of Numbers

**Natural Numbers**(also called positive integers, counting numbers, or natural numbers): They are the numbers {1, 2, 3, 4, 5, …}**Whole Numbers:**This is the set of natural numbers, plus zero, i.e., {0, 1, 2, 3, 4, 5, …}.**Integers:**This is the set of all whole numbers plus all the negatives (or opposites) of the natural numbers, i.e., {… , ⁻2, ⁻1, 0, 1, 2, …}**Rational numbers:**This is all the fractions where the top and bottom numbers are integers; e.g., 1/2, 3/4, 7/2, ⁻4/3, 4/1 [Note: The denominator cannot be 0, but the numerator can be].**Real numbers**(also called measuring numbers or measurement numbers): This includes all numbers that can be written as a decimal. This includes fractions written in decimal form e.g., 0.5, 0.75 2.45, ⁻0.074, 0.333, or 2.1443. It also includes all the irrational numbers such as π, √7 and more. Every real number corresponds to a point on the number line.

This video lays out the basics of Number Systems. Understanding this topic well is necessary to solve questions that are asked in various competitive exams in the Quant section - applicable to CAT, XAT, MAT, SNAP, IIFT, CLAT, AILET, DU LLB, any other entrance exam as well.

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