Notes for Class 6 Maths Chapter 2- Whole Numbers

CHAPTER 2 WHOLE NUMBERS
 
NATURAL NUMBERS
All numbers starting from 1 are called natural numbers.
 
PREDECESSOR AND SUCCESSOR
Subtracting 1 from a number gives its predecessor.
Adding 1 to a number gives its successor.
Note that 1, as a natural number, does not have a predecessor.
 
WHOLE NUMBERS
All the numbers from 0, 1, 2… are called whole numbers.
 
THE NUMBER LINE
Arranging the numbers on a line such that they are in an increasing order from left to right, having equal distance between them, forms a number line.
The distance between 0 and 1 is called ‘unit’ distance.
 
ADDITION USING NUMBER LINE
Consider 4+2. Start from 4 and make 2 jumps to the right. You get 6. And 4=2=6.
Therefore, to add, you move to the right.
 
SUBTRACTION USING NUMBER LINE
Consider 4-2. Start from 4 and make 2 jumps to the left. You get 2. And 4-2=2
 
MULTIPLAICATION USING NUMBER LINE
Again, consider 4x2. Start from 0 and move 4 units at a time to the right. Make 2 such moves and you’ll reach 8. And 4x2=8
 
PROPERTIES OF WHOLE NUMBERS

• The sum and product of two whole numbers is a whole number. Therefore, the Closure Property is applicable under addition and multiplication of whole numbers. However, closure property is not applicable on subtraction and division.
• Addition and multiplication of whole numbers is commutative.

E.g. 5+7= 7+5= 12
       5x7= 7x5= 35

• Addition and multiplication of whole numbers is associative.

E.g. (2+5) +4= 2+ (5+4)= 11
       (2x5) x4= 2x (5x4)= 40

• Addition and multiplication of whole numbers follow the distributive property.

E.g. 4x(2+3)= (4x2)+(4x2)= 20

• Zero is the identity element for addition of whole numbers. Zero added to any number gives the number itself.

E.g. 1+0=1

• One is the identity element for multiplication of whole numbers. One multiplied with any number gives the number itself.

E.g. 10x1=10
 
NOTE: Division by zero is not defined.