English

Properties of Whole Numbers

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Topics

  • For Addition
  • For Subtraction
  • For Multiplication
  • For Division
  • Key Points Summary
CISCE: Class 6

For Addition

Property Definition Example
Closure Property Adding two whole numbers always gives a whole number. 5 + 8 = 13,
4 + 0 = 4
Commutative Property Changing the order of addition doesn't change the sum. 4 + 3 = 7,
3 + 4 = 7
Associative Property The grouping of numbers doesn’t affect the sum.
x + (y + z) = (x + y) + z. 
3 + (5 + 6) = 14, 
(3 + 5) + 6 = 14
Existence of Identity Adding 0 to any number leaves it unchanged. 8 + 0 = 8,
15 + 0 = 15
Additive Inverse A number and its opposite add to give 0. 5 + (-5) = 0
Cancellation Law Adding and subtracting the same number cancels out the result.
x + y = x + z ⇒ `\cancel(x)` + y = `\cancel(x)` + z
x + 8 = 5 + 8 
⇒ x + `\cancel(8)` = 5 + `\cancel(8)`
⇒ x = 5
CISCE: Class 6

For Subtraction

Property Definition Example
Closure Property Subtracting two whole numbers doesn't always result in a whole number. 8 - 3 = 5 (Whole number), but 
15 - 18 = -3 (Not a whole number).
Commutative Property Subtraction doesn't work the same as addition; order matters.
x − y  `\cancel(=)`  y − x.
15 - 8 = 7, but
8 - 15 = -7.
Associative Property Subtraction does not satisfy the associative property.
x − (y − z) `\cancel(=)` (x − y) − z
15 - (10 - 7) = 12, but 
(15 - 10) - 7 = -2.
Distributive Property Subtraction distributes over multiplication.
x × (y − z) = x × y − x × z and
(y - z) × x = y × x − z × x
x = 3, y = 5, z = 2,
3 × (5 − 2) = 9 and
3 × 5 − 3 × 2 = 9
Existence of Identity No identity number exists for subtraction, but 0 is its own identity for subtraction. 5 - 0 = 5, but
0 − 5 ≠ 5
Existence of Inverse Subtraction doesn't have an inverse for non-zero whole numbers. No inverse exists for subtraction of non-zero whole numbers.
CISCE: Class 6

For Multiplication

Property Definition Example
Closure Property Multiplying two whole numbers always results in a whole number. 5 × 4 = 20 
12 × 0 = 0
Commutative Property The order of multiplication does not affect the result. 4 × 5 = 20, 5 × 4 = 20 
3 × 0 = 0, 0 × 3 = 0
Associative Property The grouping of numbers does not change the result. 4 × (8 × 10) = 320,
(4 × 8) × 10 = 320
Distributive Property Multiplication distributes over addition. 5 × (3 + 4) = 35,
5 × 3 + 5 × 4 = 35
Existence of Identity The identity for multiplication is 1. Multiplying any number by 1 gives the same number. 9 × 1 = 99 ,
15 × 1 = 15
Multiplicative Inverse The inverse of a number is the number that, when multiplied by the original number, gives 1. The inverse of 1 is 1: 1 × 1 = 1
No inverse exists for numbers like 2 in whole numbers.
Cancellation Law If both sides of an equation are multiplied by the same non-zero number, that number can be "cancelled out". 3 × a = 3 × b 
Cancel 3 → a = b
m × 7 = n × 7
cancel 7 → m = n
CISCE: Class 6

For Division

Property Definition Example
Closure Property Division of whole numbers does not always result in a whole number. 5 ÷ 8 is not a whole number. So, closure property does not exist for division.
Commutative Property Division of whole numbers is not commutative; changing the order changes the result.
x ÷ y `\cancel(=)` y ÷ x.
3 ÷ 5 ≠ 5 ÷3 
8 ÷ 13 ≠ 13 ÷ 8
Associative Property Division of whole numbers is not associative; grouping changes the result.
x ÷ (y ÷ z) `\cancel(=)` (x ÷ y) ÷ z
(10 ÷ 5) ÷ 2 = 1, but
10 ÷ (5 ÷ 2) = 4
Existence of Identity There is no identity element for division in whole numbers. No identity exists for division of whole numbers.
Existence of Inverse There is no inverse for division of whole numbers. Inverses do not exist for division.

Note:

  1.  a ÷ a = 1, i.e., 5 ÷ 5 = 1, 12 ÷ 12 = 1, 28 ÷ 28 = 1, etc.
  2.  a ÷ 1 = a, i.e., 5 ÷ 1 = 5, 16 ÷ 1 = 16, 28 ÷ 1 = 28, etc.
  3.  0 ÷ a = 0, i.e., 0 ÷ 8 = 0, 0 ÷ 23 = 0, 0 ÷ 47 = 0, etc.
  4.  a ÷ 0 is not defined, i.e., 8 ÷ 0 is not defined, 24 ÷ 0 is not defined, etc.
CISCE: Class 6

Key Points Summary

  • Whole numbers begin from 0 and go on forever.

  • They are “closed” under addition or multiplication.

  • Order and grouping do not change the sum or product.

  • 0 and 1 are the identities for addition and multiplication, respectively.

  • Subtraction or division might not give whole numbers.

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