Properties of Rational Numbers

To know the properties of rational numbers, we will consider here the general properties such as associative, commutative, distributive and closure properties, which are also defined for integers. Rational numbers are the numbers which can be represented in the form of p/q, where q is not equal to 0. Basically, the rational numbers are the fractions which can be represented in the number line. Let us go through all the properties here.

What are the properties of rational numbers?

The word rational has evolved from the word ratio. In general, rational numbers are those numbers that can be expressed in the form of p/q, in which both p and q are integers and q≠0. The properties of rational numbers are:

  • Closure Property
  • Commutative Property
  • Associative Property
  • Distributive Property
  • Identity Property
  • Inverse Property

Closure property

For two rational numbers say x and y the results of addition, subtraction and multiplication operations give a rational number. We can say that rational numbers are closed under addition, subtraction and multiplication. For example:

  • (7/6)+(2/5) = 47/30
  • (5/6) – (1/3) = 1/2
  • (2/5). (3/7) = 6/35

Do you know why division is not under closure property?

The division is not under closure property because division by zero is not defined. We can also say that except ‘0’ all numbers are closed under division.

Commutative Property

For rational numbers, addition and multiplication are commutative.

Commutative law of addition: a+b = b+a

Commutative law of multiplication: a×b = b×a

For example:

Commutative law example

Subtraction is not commutative property i.e. a-b ≠ b-a. This can be understood clearly with the following example:

 Commutative law - subtraction LHS
Whereas

 

Commutative law - subtraction RHS
The division is also not commutative i.e. a/b ≠ b/a, since,

Commutative law - Division LHS 
Whereas,

 Commutative law - Division RHS

Associative Property

Rational numbers follow the associative property for addition and multiplication.

Suppose x, y and z are rational, then for addition: x+(y+z)=(x+y)+z

For multiplication: x(yz)=(xy)z.

Example: 1/2 + (1/4 + 2/3) = (1/2 + 1/4) + 2/3

⇒ 17/12 = 17/12

And in case of multiplication;

1/2 x (1/4 x 2/3) = (1/2 x 1/4) x 2/3

⇒ 2/24 = 2/24

⇒1/12 = 1/12

Distributive Property

The distributive property states, if a, b and c are three rational numbers, then;

a x (b+c) = (a x b) + (a x c)

Example: 1/2 x (1/2 + 1/4) = (1/2 x 1/2) + (1/2 x 1/4)

LHS = 1/2 x (1/2 + 1/4) = 3/8

RHS = (1/2 x 1/2) + (1/2 x 1/4) = 3/8

Hence, proved

Identity and Inverse Properties of Rational Numbers

Identity Property: 0 is an additive identity and 1 is a multiplicative identity for rational numbers.

Examples:

  • 1/2 + 0 = 1/2    [Additive Identity]
  • 1/2 x 1 = 1/2   [Multiplicative Identity]

Inverse Property: For a rational number x/y, the additive inverse is -x/y and y/x is the multiplicative inverse.

Examples:

The additive inverse of 1/3 is -1/3. Hence, 1/3 + (-1/3) = 0

The multiplicative inverse of 1/3 is 3. Hence, 1/3 x 3 = 1

Video Lesson

 

To learn more about other topics download BYJU’S – The Learning App and watch interactive videos. Also, take free tests to practise for exams.

Frequently Asked Questions – FAQs

What are the important properties of rational numbers?

The major properties are: Commutative, Associative, Distributive and Closure property.

When two rational numbers are added then it is equal to?

Two rational numbers when added gives a rational number. For example, 2/3 + 1/2 = 7/6.

What is the distributive property of rational numbers?

The distributive property states, if a, b and c are three rational numbers, then;
a x (b+c) = (a x b) + (a x c)

The commutative property of rational number is applicable to addition and multiplication only. True or false?

True. The commutative property of rational numbers is applicable for addition and multiplication only and not for subtraction and division.

The multiplication of two rational numbers gives?

The multiplication or product of two rational numbers produces a rational number.

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