6.2 Integers


6.2 Addition and Subtraction of Integers

6.2.1 Addition of Integers
1.
Addition of integers can be done on a number line.
(a) To add a positive integer:
Move to the right (positive direction) on the number line.

(b)
To add a negative integer:
Move to the left (negative direction) on the number line.



2. Integers
with the same signs are called integers with like signs.
Example:
2 and 7, –25 and –5.

3. Integers with the different signs are called integers with unlike signs.
Example:
+2 and –7, –25 and 5.

Example 1:

Solve the following.
(a) 3 + (+4)
(b) 2 + (–5)

Solution:
(a)

Therefore,
3 + (+4) = 3 + 4
= 7

(b)
Therefore,
2 + (–5)
= –3


6.2.3 Multiplication and Division of Integers
1. Multiplication and division of like signs gives (+)

( + ) × ( + ) = + ( + ) ÷ ( + ) = + ( ) × ( ) = + ( ) ÷ ( ) = +


2.
Multiplication and division of unlike signs gives ()


( + ) × ( ) = ( + ) ÷ ( ) = ( ) × ( + ) = ( ) ÷ ( + ) =

Example:
  (a) –25 ÷ 5 = –5
  (b)   8 × (–5) = –40
 

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