Irrational Numbers – Definition with Examples
Created on Jan 04, 2024
Updated on January 4, 2024
Welcome to Brighterly’s comprehensive guide on the Irrational Numbers! In this blog post, we will embark on an exciting journey through the captivating world of mathematics. We will uncover the secrets of the Irrational Numbers, delve into the intriguing properties of irrational numbers, and master the art of multiplication and division of numbers. By the end of this journey, you will have a deeper understanding of these mathematical concepts and be equipped with the tools needed to excel in your studies. So, let’s begin our adventure and shine a Brighterly light on the fascinating world of fractions and irrational numbers!
Properties of Irrational Numbers
Irrational numbers are unique and interesting entities in the world of mathematics. These numbers cannot be expressed as a simple fraction, meaning they have a nonrepeating, nonterminating decimal representation. Some of the most famous irrational numbers are π (pi) and √2 (the square root of 2). Some important properties of irrational numbers include:
 Irrational numbers are dense on the number line: Between any two rational numbers, there will always be an irrational number.
 Irrational numbers cannot be expressed as a/b: An irrational number cannot be written as a fraction where a and b are integers, and b ≠ 0.
 An irrational number multiplied by a rational number can be irrational: For example, (2/3) * √2 is irrational.
 The sum or difference of a rational and an irrational number is irrational: For instance, 3 + √2 is irrational.
List of Irrational Numbers
There are countless irrational numbers, but some are more wellknown than others. Here is a list of some common irrational numbers:
 π (pi): The ratio of a circle’s circumference to its diameter.
 e (Euler’s number): The base of the natural logarithm.
 √2 (square root of 2): The length of the diagonal of a square with side length 1.
 Golden ratio (φ): The ratio of two quantities such that the ratio of the sum to the larger quantity is equal to the ratio of the larger quantity to the smaller one.
Set of Irrational Numbers
The set of irrational numbers, often denoted by I, is the collection of all numbers that cannot be expressed as a simple fraction. It is a subset of the real numbers, which includes both rational and irrational numbers. In mathematical notation, the set of irrational numbers can be represented as:
I = {x ∈ R  x ∉ Q}
This notation means that an irrational number x belongs to the set of real numbers (R) but not to the set of rational numbers (Q).
Are Irrational Numbers Real Numbers?
Yes, irrational numbers are real numbers! The set of real numbers (R) includes both rational (Q) and irrational (I) numbers. Real numbers can be visualized on a number line, and irrational numbers are densely scattered among rational numbers on this line.
Sum and Product of Two Irrational Numbers
The sum and product of two irrational numbers can be either rational or irrational. For example, consider the following cases:
 (√2 + √3) is an irrational number.
 (√2 * √3) = √6, which is an irrational number.
 (√2 + (√2)) = 0, which is a rational number.
 (√2 * √2) = 2, which is a rational number.
Differences Between Rational and Irrational Numbers
Rational and irrational numbers have some key differences. Rational numbers can be expressed as a fraction (a/b) where a and b are integers, and b ≠ 0. Irrational numbers, on the other hand, cannot be expressed as a simple fraction. Some key differences between rational and irrational numbers include:
 Decimal representation: Rational numbers have either a terminating or repeating decimal representation, while irrational numbers have a nonterminating, nonrepeating decimal representation.
 Density: Irrational numbers are dense on the number line, meaning there is always an irrational number between any two rational numbers.
 Algebraic representation: Rational numbers can be roots of linear equations with integer coefficients, whereas irrational numbers are often the roots of higherdegree polynomial equations with integer coefficients.
Multiplication of Twodigit Number by Onedigit Number
Multiplying a twodigit number by a onedigit number is an essential skill for children to learn. It involves breaking down the twodigit number into tens and ones, multiplying each part by the onedigit number, and then adding the results. Here’s a stepbystep process:
 Break the twodigit number into tens and ones.
 Multiply the tens part by the onedigit number.
 Multiply the ones part by the onedigit number.
 Add the products obtained in steps 2 and 3.
For example, let’s multiply 24 by 3:
 Break 24 into 20 (2 tens) and 4 (4 ones).
 Multiply 20 by 3: 20 * 3 = 60.
 Multiply 4 by 3: 4 * 3 = 12.
 Add the products: 60 + 12 = 72.
So, 24 * 3 = 72.
Division without Remainder
Division without remainder occurs when the dividend is exactly divisible by the divisor. In this case, there is no leftover amount after dividing the dividend into equal groups. The quotient represents the exact number of groups or parts.
For example, let’s divide 20 by 4:
 Create a rectangle representing 20 and divide it into rows of 4 (the divisor).
 Count the number of rows: There are 5 rows of 4.
 The number of rows represents the quotient: 5.
So, 20 ÷ 4 = 5, with no remainder.
Irrational Number Theorem and Proof
The Irrational Number Theorem states that the square root of a nonperfect square positive integer is irrational. A common proof for this theorem is a proof by contradiction, which involves assuming that the square root of a nonperfect square positive integer is rational and then showing that this assumption leads to a contradiction.
For example, let’s prove that √2 is irrational:
 Assume that √2 is rational, so it can be written as a fraction a/b, where a and b are integers with no common factors other than 1, and b ≠ 0.
 (√2)² = (a/b)² => 2 = a²/b² => 2b² = a².
 Since a² is even (2b²), a must be even. Let a = 2k, where k is an integer.
 Substitute a = 2k into 2b² = a² => 2b² = (2k)² => b² = 2k².
 Since b² is even (2k²), b must also be even.
 Since both a and b are even, they share a common factor of 2, which contradicts the assumption that they have no common factors other than 1.
Therefore, the assumption that √2 is rational is false, proving that √2 is irrational.
How to Find an Irrational Number?
To find an irrational number between two given numbers, you can use the following method:
 Calculate the average of the two numbers.
 If the average is irrational, you have found an irrational number between the two given numbers.
 If the average is rational, add a small irrational value, such as √2, to the average to obtain an irrational number between the two given numbers.
For example, let’s find an irrational number between 2 and 3:
 Calculate the average: (2 + 3) / 2 = 2.5.
 Since 2.5 is rational, add √2: 2.5 + √2 ≈ 3.9142.
 The irrational number 3.9142 lies between 2 and 3.
Irrational Numbers Solved Examples
Here are some examples of operations involving irrational numbers:

 √2 + √3 ≈ 3.1463 (sum of two irrational numbers)
 √2 * √3 = √6 (product of two irrational numbers)
 2 + √3 ≈ 3.7321 (sum of a rational and an irrational number) 4. 2 * √3 ≈ 3.4641 (product of a rational and an irrational number)
Practice Questions on Irrational Numbers
 Simplify (√5 + √2)².
 Prove that √3 is irrational.
 Find an irrational number between 1 and 2.
 Calculate the product of √7 and √14.
Conclusion
Throughout this article, we have navigated the intricate landscape of the irrational numbers of fractions and its applications across various mathematical operations, including multiplication and division of whole numbers, decimals, and fractions. We have also ventured into the mysterious realm of irrational numbers, unraveling their properties and distinguishing them from their rational counterparts.
With a Brighterly perspective, we have illuminated these essential mathematical concepts, empowering children to build a strong foundation for future success in mathematics. By understanding and mastering these ideas, they will be better equipped to tackle more complex mathematical challenges, fostering a lifelong love for learning and growth.
At Brighterly, we believe in nurturing the potential of every child, and through our engaging and interactive approach to learning, we aim to inspire a generation of bright and curious minds. Let us continue to explore the wonders of mathematics together, building a Brighterly future for all!
Frequently Asked Questions on Irrational Numbers
What is an irrational number?
An irrational number is a number that cannot be expressed as a simple fraction (a/b) where a and b are integers, and b ≠ 0. Irrational numbers have nonterminating, nonrepeating decimal representations.
Are irrational numbers real numbers?
Yes, irrational numbers are real numbers. The set of real numbers is comprised of both rational and irrational numbers.
Can irrational numbers be written as decimals?
Yes, irrational numbers can be written as decimals. However, their decimal representations are nonterminating (neverending) and nonrepeating.
Can irrational numbers be written as fractions?
No, irrational numbers cannot be expressed as simple fractions (a/b) where a and b are integers, and b ≠ 0. This is one of the defining characteristics of irrational numbers.
What are some examples of irrational numbers?
Some common examples of irrational numbers include:
 √2, the square root of 2
 √3, the square root of 3
 π (pi), the ratio of a circle’s circumference to its diameter
 e, the base of the natural logarithm
Can the sum of two irrational numbers be rational?
Yes, the sum of two irrational numbers can be rational. For example, √2 and √2 are both irrational, but their sum (√2 + √2) is 0, which is rational.
Can the product of two irrational numbers be rational?
Yes, the product of two irrational numbers can be rational. For example, √2 and √2 are both irrational, but their product (√2 * √2) is 2, which is rational.
How can you find an irrational number between two given numbers?
To find an irrational number between two given numbers, calculate their average and add a small irrational value, such as √2, if the average is rational. For example, to find an irrational number between 1 and 2, calculate the average (1.5), and add √2: 1.5 + √2 ≈ 2.9142.
Information Sources
The information in this article was compiled from the following reliable sources: