What are irrational numbers in math?

What are irrational numbers in math? : Irrational numbers are any real numbers that cannot be expressed as the ratio of two integers , p/q, where p and q are both integers . For instance, the square root of 2 cannot be represented by an integer or a fraction.
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Irrational numbers are real numbers that cannot be represented as simple fractions. An irrational number cannot be expressed as a ratio, such as p/q, where p and q are integers, q≠0. It is a contradiction of rational numbers. Irrational numbers are usually expressed as R\Q, where the backward slash symbol denotes ‘set minus’. It can also beexpressed as R – Q, which states the difference between a set of real numbers and a set of rational numbers.

The calculations based on these numbers are a bit complicated. For example, √5, √11, √21, etc., are irrational. If such numbers are used in arithmetic operations, then first, we need to evaluate the values under the root. These values could sometimes be recurring also. Now let usfind out its definition, lists of irrational numbers, how to find them, etc., in this article.

Table of Contents

What are Irrational Numbers?

An irrational number is a real number that cannot be expressed as a ratio of integers; for example, √2 is an irrational number.  We cannot express any irrational number in the form of ratio, such as p/q, where p and q are integers, q≠0. Again, the decimal expansion of an irrational number is neitherterminating nor recurring

Irrational Meaning: The meaning of irrational is not having a ratio or no ratio can be written for that number. That means the number cannot be expressed other than using roots. In other words, we can say that irrational numbers cannot be represented as the ratio of two integers.

What are the examples of Irrational numbers?

The real numbers which cannot be expressed in the form of p/q, where p and q are integers and q ≠ 0 are known as irrational numbers. For example  √2 and √ 3 etc. are irrational. Whereas any number which can be represented in the form of p/q, such that, p and q are integers and q ≠ 0 is known as a rational number.

Is Pi an irrationalnumber?

Pi (π) is an irrational number because it is non-terminating. The approximate value of pi is 22/7. Also, the value of π is 3.14159 26535 89793 23846 264…

Irrational Number Symbol

Generally, the symbol used to represent the irrational symbol is “P”.  Since irrational numbers are defined negatively, the set of real numbers (R) that are not the rational number (Q) is called anirrational number. The symbol P is often used because of the association with the real and rational number. (i.e.,) because of the alphabetic sequence P, Q, R. But mostly, it is represented using the set difference of the real minus rationals, in a way R- Q or R\Q.

Since irrational numbers are the subsets of real numbers, irrational numbers will obey all the properties of the real number system. The following are the properties of irrational numbers:

  • The addition ofan irrational number and a rational number gives an irrational number.  For example, let us assume that x is an irrational number, y is a rational number and the addition of both the numbers x +y gives a rational number z.
  • Multiplication of any irrational number with any nonzero rational number results in an irrational number. Let us assume that if xy=z is rational, then x =z/y is rational, contradicting the assumption that x is irrational. Thus, the product xy must beirrational.
  • The least common multiple (LCM) of any two irrational numbers may or may not exist.
  • The addition or the multiplication of two irrational numbers may be rational; for example, √2. √2 = 2. Here, √2 is an irrational number. If it is multiplied twice, then the final product obtained is a rational number. (i.e) 2.
  • The set of irrational numbers is not closed under the multiplication process, unlike the set of rational numbers.

Listof Irrational Numbers

The famous irrational numbers consist of Pi, Euler’s number, Golden ratio. Many square roots and cube roots numbers are also irrational, but not all of them. For example, √3 is an irrational number, but √4 is a rational number. Because 4 is a perfect square, such as 4 = 2 x 2 and √4 = 2, which is a rational number.  It should be noted that there are infinite irrational numbers between any two real numbers. For example, say 1 and 2, there areinfinitely many irrational numbers between 1 and 2. Now, let us look at famous irrational numbers’ values.

Pi, π  3.14159265358979…
Euler’s Number, e 2.71828182845904…
Golden ratio, φ 1.61803398874989….

Are Irrational Numbers Real Numbers?

In Mathematics, all irrational numbers are considered real numbers, which should not be rational numbers. It means irrational numbers cannot be expressed as the ratio of two numbers. The irrational numbers can be expressed as non-terminating fractions and in different ways. For example, the square roots that are not perfect will always result in an irrational number. 

Sum and Product of Two Irrational Numbers

Now, let us discuss the sum and the product of irrational numbers.

Product of Two Irrational Numbers

Statement: The product of two irrational numbers is sometimes rational or irrational

For example, √2 is an irrational number, but when √2  is multiplied by√2, we get the result 2, which is a rational number.

(i.e.,) √2 x √2 = 2 

We know that π is also an irrational number, but if π is multiplied by π, the result is π2, which is also an irrational number.

(i.e..) π x π = π2

It should be noted that while multiplying the two irrational numbers, it may result in an irrational number or a rational number. 

Sum of Two Irrational Numbers

Statement: The sum of two irrational numbers is sometimes rational or irrational.

Like the product of two irrational numbers, the sum of two irrational numbers will also result in a rational or irrational number.

For example, if we add two irrational numbers, say 3√2+ 4√3, a sum is an irrational number.

But, let us consider another example, (3+4√2) + (-4√2 ), the sum is3, which is a rational number.

So, we should be very careful while adding and multiplying two irrational numbers, because it might result in an irrational number or a rational number.

Irrational Number Theorem and Proof

The aforementioned claim is supported by the subsequent theorem.

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Theorem: Given p is a prime number and a2 is divisible by p, (where a is any positive integer),then it can be concluded that p also divides a.

Proof: Using the Fundamental Theorem of Arithmetic, the positive integer can be expressed in the form of the product of its primes as:

a = p1 × p2 × p3………..  × pn …..(1)

Where, p1, p2, p3, ……, pn represent all the prime factors of a.

Squaringboth the sides of equation (1),

a2 = (p1 p2 p3. pn) (p1 p2 p3. pn).

⇒a2 = (p1)2 × (p2)2 × (p3 )2………..× (pn)2

The prime factorization of a natural number is distinct, with the exception of the factors’ order, according to the Fundamental Theorem of Arithmetic.

The only prime factors of a2 are p1, p2, p3……….., pn. If p is a prime number and a factor of a2, then p is one of  p1, p2 , p3……….., pn.So, p will also be a factor of a.

Hence, if a2  is divisible by p, then p also divides a.

Now, using this theorem, we can prove that 2 is irrational.

How to Find an Irrational Number?

Let us find the irrational numbers between 2 and 3. We know square root of 4 is 2; √4=2 and the square root of 9 is 3; √9 = 3 Therefore, the number of irrational numbers between 2 and 3 are 5, 6, 7, and 8, as these are not perfect squares and cannot be simplified further. Similarly, you can also find irrational numbers, between any other two perfect square numbers.

Another case:

Let us assume a case of 2. Now, how can we find if 2is an irrational number?

Suppose 2 is a rational number. Then, by the definition of rational numbers, it can be written that,

2 =p/q    …….(1)

Where p and q are co-prime integers, and q is zero. (Co-prime numbers are those whose common factor is 1).

Squaring both sides of equation (1), we have

2 = p2/q2

⇒ p2 = 2 q 2   ………. (2)

From the theorem stated above, if 2 is a prime factor of p2, then 2 is also a prime factor of p.

P therefore equals 2c, where c is an integer.

Substituting this value of p in equation (3), we have

(2c)2 = 2 q 2

⇒ q2 = 2c 2 

This implies that 2 is a prime factor ofq2 also. Again from the theorem, it can be said that 2 is also a prime factor of q.

According to the initial assumption, p and q are co-primes but the result obtained above contradicts this assumption as p and q have 2 as a common prime factor other than 1. This contradiction arose due to the incorrect assumption that 2  is rational.

So, root 2 is irrational.

Similarly, we can justify the statement discussed in the beginning that if p is a prime number, then  p  is an irrational number. Similarly, it can be proved that for any prime number p, p is irrational.

Irrational Numbers Solved Examples

Question 1: Which of thefollowing are Rational Numbers or Irrational Numbers?

2, -.45678…, 6.5,  3,  2

Solution: Rational Numbers – 2, 6.5 as these have terminating decimals.

Irrational Numbers – -.45678…,  3,  2 as these have a non-terminating non-repeating decimal expansion.

Question 2: Check if below numbers are rational or irrational. 

2, 5/11, -5.12, 0.31 

Solution: Since the decimal expansion of a rational number either terminates or repeats. So, 2, 5/11, -5.12, 0.31 are all rational numbers.

To know more about rational and irrational numbers, download BYJU’S-The Learning App or  Register with us to watch interesting videos on irrational numbers.

Frequently Asked Questions (FAQs) on Irrational Numbers

What is an irrational number? Give an example.

An irrational number is a type of real number which cannot be represented as a simple fraction. It cannot be expressedin the form of a ratio. If N is irrational, then N is not equal to p/q where p and q are integers and q is not equal to 0. Example: √2, √3, √5, √11, √21, π(Pi) are all irrational.

Are integers irrational numbers?

Integers are rational numbers but not irrational. All theintegers whether they are positive or negative or zero can be written in the form of p/q. Example: 2, 3 and 5 are rational numbers because we can represent them as 2/1, 3/1 and 5/1.

Is an irrational number a real number?

Yes, an irrational number is a real number and nota complex number, because it is possible to represent these numbers in the number line.

What are the five examples of irrational numbers?

There are many irrational numbers that cannot be written in simplified form. Some of the examples are: √8, √11, √50, Euler’s Number e= 2.718281, Golden ratio, φ= 1.618034.

What are the main irrational numbers?

These are the most typical irrational numbers: Pi () = 22/7 = 3. Eulers Number: 14159265358979, where e = 2. Golden ratio: 71828182845904, or 1. 61803398874989. Root, = 2, 3, 5, 7, or any other number under root that cannot be further simplified.

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What are irrational numbers in math?

What are the irrational numbers give example? : A real number that cannot be represented by a straightforward fraction is said to be irrational. It cannot be described as a ratio. If N is irrational, then N is not equal to p/q, where p and q are integers and q is not equal to 0. For instance, the numbers 2, 3, 5, 11, and 21 (Pi) are all illogical.
Is 7 a irrational number? : The number seven is a logical one. When two integers are divided, the resulting number is said to be rational.
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A rational number is one that can be expressed in the form p/q, where q is not equal to zero, whereas an irrational number is one that cannot be expressed in the form p/q. The term “irrational number” can also refer to a number that continues past the decimal point without ending. Knowing what rational and irrational numbers are now, let’s examine the in-depth discussion and demonstrate why root 7 is an irrational number.

The square root of 7 will be an irrational number if the square root of 7 gives a value after decimal that is non-terminating and non-repeating. Before going forward, let us discuss quickly, the root of the number “n”. The square root of a number n is denoted by thesymbol √n. As we multiply the root of a number to itself it gives the original number whose root we have taken. Therefore,  √7 on multiplication to itself gives the number 7.

Knowing that a decimal number is irrational when its value neither terminates nor repeats is common knowledge. The answer to 7 is 2. 64575131106. It is obvious that the value of root 7 is also non-terminating and non-repeating. The requirement that 7 be an irrational number is met by this. Therefore, 7 is an irrational number.

 

Prove That Root 7 is Irrational by Contradiction Method

By employing the contradiction method as well, we can demonstrate that root 7 is irrational.

To prove: We want to prove that root 7 is irrational. Proof: We will start with the contradictory statement of what we have to prove.Let us assume that square root 7 is rational.

Now that it is a rational number, it can be expressed as p/q, where p is a prime number, q is a prime number, and i is a coprime number. e. , GCD (p,q) = 1.

p = 7q——- (1) is the result of rearranging the terms, which is 7=p/q.

On squaring both sides we get,  ⇒ p2 = 7 q2  Again rearrangingthe terms, ⇒ p2/7 = q2 ——- (2)

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The prime number 7 is well known. Using the theory, which states that it is also true that if a prime number k divides m2, then it also divides m. This implies that since 7 is a factor of p2, it must also be a factor of p.

Thus we can write p = 7a (where a is some constant)

When p = 7a is substituted in equation (2), we obtain (49a2)/7= q2, (49a2)/7= q2, (7a)2/7= q2, and (a2)= q2/7 ——- (3).

This demonstrates that the number seven will also be a factor in q. Assuming that p and q are coprime numbers, the only number that can divide them both equally is 1, which is why this initial assumption was made. But in this case, 7 is the common factor of p and q, which runs counter to what we first believed.

This disproves the notion that root 7 is a rational number. The square root of 7 is irrational as a result.

Prove That Root 7 is Irrational by Long Division Method

The long division method is another way to demonstrate that the root of 7 is irrational. In order to determine whether we obtained the non-terminating and non-repeating value after the decimal or not, we used the long division method to calculate the value of the root of 7.

The long division method can be applied using the following steps:

  • Step 1: Add pairs of 0 after 7 as 7.00 00 00 and pair the digits starting from the right and find a number whose square is less than or equal to the number 7, it will be our first divisor and quotient. We have 2 square the number and subtract the result from 7, 3 is the remainder. 
  • Step 2: Take the next pair of 0 down after the remainder, as 00 is brought down, we get 300 as the next dividend, and double the first quotient to get the partial divisor of this step. The unit digit the divisor will be the number which on multiplying with the complete divisor thus formed, gives a number equal or less than the new dividend. Here, we get 6 at the units place, and 46 is our divisor and 6 is our quotient.Subtract the result after multiplying 46 with 6 from 300, and note down the remainder.   
  • Step 3: Take the next pair of 0 down after the remainder of the previous step to get the dividend, 2400 is the new dividend. Add the units place of the divisor obtained in the previous step to the divisor itself and get the partial divisor of this step. Here, we get 52. The unit digit the divisor will be the number which on multiplying with thecomplete divisor thus formed, gives a number equal or less than the new dividend. Here, we get 4 at the units place, and 524 is our divisor and 4 is our new quotient. Subtract the result after multiplying 524 with 4 from 2400, and note down the remainder.   
  • Step 4: Repeat the process until the required number of digits after the decimal is obtained.

A few of the steps in the long division of 7 are shown in the following image.

As we can see the value of root 7 does not terminate after 3 decimal places. It can still be extended further. Hence, this makes √7 an irrational number.

☛ Also Check:

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  • Prove that Root 2 is Irrational
  • Prove that Root 3 is Irrational
  • Prove that Root 5 is Irrational
  • Prove that Root 6 is Irrational
  • Prove that Root 11 is Irrational

FAQs on Is Root 7 an Irrational?

How do you Prove that Root 7 is Irrational?

We can prove that root 7 is an irrational number by usingvarious methods like the long division method, and method of contradiction. Also, the square root of 7 will be an irrational number if it gives a value after the decimal point that does not terminate and does not repeat. The value of root 7 is 2.64575131106…it is clear that it is non-terminating and nonrepeating, hence √7 anirrational number.

Is 2 times the Square Root of 7 Irrational?

Yes, 2 times the square root of 7 is irrational. To find out whether 2 times the square root of 7 is an irrational number, we multiply both the numbers and check the result. On multiplying 2 with root 7, we get 2 × 2.64575131106… = 5.29150262212.. which is a non-terminating and non-repeating term,therefore the product of the two is an irrational number. 

How to Prove Root 7 is Irrational by Contradiction?

We can prove it by using the contradiction method where we assume the root 7 as the rational number and write it as the ratio of two coprime numbers (p/q) and proceed further if we can find any common factor of the coprime numbers thus assumed, which will prove that the root 7 is irrational.  To prove root 7 is irrational using contradiction we usethe following steps:

  • Step 1: Assume that √7 is rational.
  • Step 2: Hence, √7 = p/q
  • Step 3: Now both sides are squared, simplified and a constant value is substituted.
  • Step 4: It is found that 7 is a factor of the numerator and the denominator which contradicts the property of a rational number.

Therefore it is proved that root 7 is irrational by the contradiction method. 

Is 3 Times the Square Root of 7 Irrational?

Yes, 3 times the square root of 7 is an irrational number. 3 times the square root 7 is written as 3 × √7 = 3 ×2.64575131106… = 7.93725393318… Here, we get the result that is nonterminating as well as nonrepeating. Thus, we can also conclude that any rational number multiplied with root 7 will be irrational. Hence, 3 times the square root of 7 is irrational too.

How to Prove that 1 by Root 7 is irrational?

We can prove 1 by root 7 is irrational using various methods, such as directly finding the value of 1 by root 7 and checking whether the result is non-terminating and non-recurring or not, or by using the method of contradiction. Let us prove that by finding the value of 1/√7. The value of 1/√7 is 0.377964473.. which extends to infinity and the terms are nonterminating as well as nonrepeating, hence we can clearly say that 1/√7 is an irrational number.

[/lightweight-accordion]How do you know if a number is irrational? : Irrational is a term used to describe all non-rational numbers. A fraction cannot be used to represent an irrational number, but it can be written as a decimal. A number that is irrational has an infinite number of non-repeating digits to the right of the decimal point.
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Numbers are only a small part of mathematics. There are applications in a wide range of fields, from physics to physical education, and it includes shapes, logic, symbols, spaces, and general skills like precision attention and critical thinking. But if you ask someone what math is, they will almost always mention numbers in their response. They frequently serve as both our introduction to math and a clear example of how math is used in everyday life.

It is not an easy question to answer. It was not always known, for example, how to write and perform arithmetic with zero or negative quantities. The notion of number has evolved over millennia and has, at least apocryphally, cost one ancient mathematician his life.

Natural, Whole, and Integer Numbers

The most commonnumbers that we encounter—in everything from speed limits to serial numbers—are natural numbers. These are the counting numbers that start with 1, 2, and 3, and go on forever. If we start counting from 0 instead, the set of numbers are instead called whole numbers.

These are common terms, but this is also an opportunity to discuss how math is ultimately a human endeavor. Open it up to your students: what would they call the set of numbers 1, 2, and 3? What new name would they give it if they added 0?.

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The integer numbers (or simply integers) extend whole numbers to their opposites too: …–3, –2, –1, 0, 1, 2, 3…. Notice that 0 is the only number whose opposite is itself.

Expanding the concept of number further brings us to rational numbers. The name has nothing to do with the numbers being sensible, although it opens up a chance to discuss ELA in math class and show how one word can have many different meanings in alanguage and the importance of being precise with language in mathematics. Rather, the word rational is related to the word found within the first five letters: ratio.

A rational number is any number that can be written as the ratio of two integers, such as \(\frac{1}{2}\), \(\frac{783}{62,450}\) or \(\frac{-25}{5}\). Note that while ratios can always be expressed as fractions, they can appear in different ways, too. For example, \(\frac{3}{1}\) is usuallywritten as simply \(3\), the fraction \(\frac{1}{4}\) often appears as \(0.25\), and one can write \(-\frac{1}{9}\) as the repeating decimal \(-0.111\)….

Any number that cannot be written as a rational number is, logically enough, called an irrational number. And the entire category of all of these numbers, or in other words, all numbers that can be shown on a number line, are called real numbers. The hierarchy of realnumbers looks something like this:

An important property that applies to real, rational, and irrational numbers is the density property. It says that between any two real (or rational or irrational) numbers, there is always another real (or rational or irrational) number. For example, between 0.4588 and 0.4589 exists the number 0.45887, along with infinitely many others. And thus, here are all the possiblereal numbers:

Real Numbers: Rational

Understand a rational number as the relationship between two integers and where it falls on a number line. (Grade 6).

Rational Numbers: Any number that can be written as a ratio (or fraction) of two integers is a rational number. It is common for students to ask, are fractions rational numbers? The answer is yes, but fractions make up a large category that also includes integers, terminating decimals, repeating decimals,and fractions.

  • An integer can be written as a fraction by giving it a denominator of one, so any integer is a rational number.\(6=\frac{6}{1}\)\(0=\frac{0}{1}\)\(-4=\frac{-4}{1}\) or \(\frac{4}{-1}\) or \(-\frac{4}{1}\)
  • A terminating decimal can be written as a fraction by using properties of place value. For example, 3.75 = three and seventy-five hundredths or \(3\frac{75}{100}\), which is equal to the improper fraction \(\frac{375}{100}\).
  • A repeating decimal can always be written as a fraction using algebraic methods that are beyond the scope of this article. However, it is important to recognize that any decimal with one or more digits that repeats forever, for example \(2.111\)… (which can be written as \(2.\overline{1}\)) or \(0.890890890\)… (or \(0.\overline{890}\)), is a rational number. A common question is “are repeating decimals rational numbers?” The answer is yes!

Integers:The counting numbers (1, 2, 3,…), their opposites (–1, –2, –3,…), and 0 are integers. A common error for students in Grades 6–8 is to assume that the integers refer to negative numbers. Similarly, many students wonder, are decimals integers? This is only true when the decimal ends in “.000…,” as in 3.000…, which is equal to 3. (Technically it is also true when a decimal ends in “.999…” since 0.999… = 1. This doesn’t come up particularly often, but the number 3 can in fact be writtenas 2.999….)

Whole Numbers: Zero and the positive integers are the whole numbers.

Natural Numbers: Also called the counting numbers, this set includes all of the whole numbers except zero (1, 2, 3,…).

Real Numbers: Irrational

Important standard: Be aware that some numbers are irrational. (Grade 8).

Irrational Numbers: Any real number that cannot be written in fraction form is an irrationalnumber. These numbers include non-terminating, non-repeating decimals, for example \(\pi\), 0.45445544455544445555…, or \(\sqrt{2}\). Any square root that is not a perfect root is an irrational number. For example, \(\sqrt{1}\) and \(\sqrt{4}\) are rational because \(\sqrt{1}=1\) and \(\sqrt{4}=2\), but \(\sqrt{2}\) and \(\sqrt{3}\) are irrational. All four of these numbers do name points on the number line, but they cannot all be written as integer ratios.

Non-Real Numbers

Sowe’ve gone through all real numbers. Are there other types of numbers? For the inquiring student, the answer is a resounding YES! High school students generally learn about complex numbers, or numbers that have a real part and an imaginary part. They look like \(3+2i\) or \(\sqrt{3}i\) and provide solutions to equations like \(x^2+3=0\) (whose solution is \(\pm\sqrt{3}i\)).

In some sense, complex numbers mark the “end” of numbers, although mathematicians are alwaysimagining new ways to describe and represent numbers. Numbers can also be abstracted in a variety of ways, including mathematical objects like matrices and sets. Encourage your students to be mathematicians! How would they describe a number that isn’t among the types of numbers shown here? Why might a scientist or mathematician try to do this?

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Check out HMH Into Math, our core math solution for Grades K–8, if you’re looking for a math curriculum that will increase student confidence in mathematics and assist learners in using rational and irrational numbers.

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Additional Question — What are irrational numbers in math?

Is 4/5 an irrational number?

4/5 is a rational fraction. By dividing two integers by two, rational numbers are produced. Integers, another term for whole numbers, include both 4 and 5.

Is 2/3 A irrational number?

In mathematics rational means “ratio like.” So a rational number is one that can be written as the ratio of two integers. For example 3=3/1, −17, and 2/3 are rational numbers.

Is 5/3 an irrational number?

5/3 is a rational number, yes. Even though the fraction 5/3 would be represented as a repeating decimal of 1, if expressed in decimal form. 66666

Is 2 √ 3 a rational or irrational number?

A nonsensical number is (2) – (3).

Is 5 a irrational number?

The number 5 is not an irrational number Real numbers: Real numbers can be defined as the union of both the rational and irrational numbers They can be both positive or negative and are denoted by the symbol R

Is √ 3 an irrational number?

It is illogical to square the number three. As a result of the radical form’s impossibility of further simplification, it is regarded as a surd. Show that root 3 is an irrational number. 1. An irrational number, Root 3, is 2. Establish the Irrationality of Root 3 Using the Contradiction Method3. Using the long division method, establish that Root 3 is irrational.

Is √ 5 is an irrational number?

The number 5 is irrational.

Is 2 a rational or irrational?

Because it meets the criteria for a rational number and can be written in p/q form, which is mathematically represented as 2/1, where 10, 2, and 10 are the prime factors, 2, is a rational number.

Is √ 9 an irrational number?

(9), a number, is logical.

Is √ 7 a rational or irrational number?

The number seven is illogical.

Is √ 4 a rational or irrational number?

Since 2 is a whole number and all whole numbers are rational, the given number 4 is equal to 2 in this case. As a rational number, it can also be expressed in fractional form as 2 1 4 is therefore not an irrational number.

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