KCSE ONLINE

Esoma Online Revision Resources

Integers - Mathematics Form 1

ADDITION AND SUBTRACTION OF INTEGERS

BACKGROUND KNOWLEDGE

Numbers - whole numbers and integers.

a). Which of the following are whole numbers?

- 3, 3, 0.55, 102, 6, 9, -1.5, 0, -6

Solution


The whole numbers are -3,3, 102, 6, 9, -6 and 0

b). Identify the integers represented by the letters a, b, c and d


Solution

a is 3, b is -1, c is -2, d is -4

Note: On the number line, numbers are marked at unit integers, that is, equal single steps increasing from zero (0) to the right.

The arrow head shows the direction in which the numbers increase or decrease.

The left of zero (0) on a number line are negative numbers.
If the two numbers on a number line are taken, the one to the right is the greater one.
Note: -3 is less that -2 and 5 is less than 6


1.Choose the greater number in each of the following pairs:

a) -7,-2

b) -1, 4

c) 0, -3

d) 3, 8

Solutions

a) -2

b) 4

c) 0

d) 8


2. Addition and subtraction of whole numbers


 Practice Exercise worked out examples

Observe carefully how these are worked out

Work out the following using a number line

 

a). (+2) + (+5)

  

b). (+2) + (+2) + (+1)

  

  d). (-5) + (+2) 

 

e). (-6) + (+2) + (+4)

 

Lesson objective

By the end of this lesson you should be able to:

add integers using numberline correctly

subtract integers using number line correctly

Addition of Integers

Brackets

Brackets should be used around negative numbers to separate the minus sign attached to the number from the arithmetic operation symbol.for example, 5 - -3 should be written as 5 -(-3) and 7 x -2 should be written as 7 x (-2).

Note :Never write two arithmetic operations symbols together without using brackets.



N.B

When adding a positive number to an integer

using a number line start from the first number

and move right a number of steps equal to the

integer being added.


INTRODUCTION


Work out the following using a number line:

a). (+6) + (-4)  

b). (+7) + (-2) + (-1)

c). (-4) + (-3) 

d). (-3) + (-2) + (-1)

 

Exercise

Work out the following using the number line:

a). (+3) - (-4)

  

 

 b). (-5) - (-2) - (-3)

 

 

 c). (-7) - (-4)

 

 

 

d). (+2) - (-3) - (-1)

 

 

 

 

INTEGERS

In our daily lives we always deal with integers .

Discover how useful they are

In our daily we always deals

discover how useful they are

b) Work out (-2) + (-5) using a number line

When adding a negative integers start from the

first number and move left a number of steps

equal to the integers being added

SUBTRACTION OF INTEGERS

When subtracting a positive number from an integer using a number line, start from the first number and move left a number of steps equal to the integer being subtracted.

Case3 Example 1 Work out (+4) - (+7) using number line


   

 

When subtracting a positive number from an integer  using a number line, start from the first number and move left a number of steps equal to the integer being subtracted.   Work out the following using the number line

a). (+10) - (+3)


            


            b). (+ 9) - (+2) - (+1)


   


  c). (- 6)- (+ 3)


   

     

  Case 4

Subtraction of negative integers

Work out (+5) - (-3) using a number line

 


 


   Work out (-4) - (-5) using a number line

 

   

When subtracting a negative number from an

 
integer using the number line start from the

 
first number and move right to a number of

 
steps equal to the integer being subtracted.


 

NB. When subtracting an integer from another

 
using the number line, the following steps can

be followed:


1.Find the difference between the two numbers


2.Determine the direction you move from the

 
second number to first. 

3.If to the right the answer is positive and if to the left the answer is negative

REMEMBER


That subtracting a negative integer from any number is the   

same as adding an equivalent positive integer.    e.g (-7) - (- 4) = (-7 ) + (+4) = -3.

Subtracting a positive number from any number is the same

as adding an equivalent negative integer.  e.g (+3) - (+4) = (+3) + (-4) = -1


SUBTRACTION OF INTEGERS

When subtracting a positive number from an integer using a number line, start from the first number and move left a number of steps equal to the integer being subtracted.

Case3 Example

Work out (+4) - (+7) using number line

 

When subtracting a positive number from an integer using a number line, start from the first number and move left a number of steps equal to the integer being subtracted.Work out the following using the number line.

 


Subtraction of negative integers

Work out (+5) - (-3) using a number line

Work out (-4) - (-5) using a number line

Order this CD Today to Experience the Full Multimedia State of the Art Technology!

For Best results INSTALL Adobe Flash Player Version 16 to play the interactive content in your computer. Test the Sample e-Content link below to find out if you have Adobe Flash in your computer.

Sample Coursework e-Content CD

Other Goodies for KCSE ONLINE Members!

Coursework e-Content CD covers all the topics for a particular class per year and costs 1200/- ( Per Subject per Class ).

Purchase Online and have the CD sent to your nearest Parcel Service. Pay the amount to Patrick 0721806317 by M-PESA then provide your address for delivery of the Parcel. Alternatively, you can use BUY GOODS TILL NUMBER 827208 Ask for clarification if you get stuck.

Install ADOBE Flash Player for Best Results

For Best results INSTALL Adobe Flash Player Version 16 to play the interactive content in your computer. Test the link below to find out if you have Adobe Flash in your computer.

Search

Subject Menu