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JSS1: MATHEMATICS - 1ST TERM

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  1. Whole Numbers I | Week 1
    3Topics
    |
    1 Quiz
  2. Whole Numbers II | Week 2
    1Topic
    |
    1 Quiz
  3. Counting in Base Two | Week 3
    4Topics
    |
    1 Quiz
  4. Arithmetic Operations | Week 4
    3Topics
    |
    1 Quiz
  5. Lowest Common Multiple (LCM) | Week 5
    1Topic
    |
    1 Quiz
  6. Highest Common Factor | Week 6
    1Topic
    |
    1 Quiz
  7. Fraction | Week 7
    7Topics
    |
    1 Quiz
  8. Basic Operations with Fractions I | Week 8
    3Topics
    |
    1 Quiz
  9. Basic Operations with Fractions II | Week 9
    1Topic
    |
    1 Quiz
  10. Directed Numbers | Week 10
    3Topics
    |
    1 Quiz
  11. Estimation and Approximation I | Week 11
    3Topics
    |
    1 Quiz
  12. Estimation and Approximation II | Week 12
    6Topics
    |
    1 Quiz
Lesson Progress
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You can add and subtract direct numbers without drawing the number line using the rules below:

The rules for addition and subtraction are:

Replace the same signs that appear together with a positive sign:  

additon1 e1605973803612

  e.g.    +5   +  ( + 3 )   =  5  +  3    =  8

Same sign gives  +

  e.g.  + 7   ( 4 )   =    7   +  4   =  11

Same sign gives  +

In other words   \( \scriptsize + \; \times \; + = + \\ \scriptsize – \; \times \; – \; = + \)

Replace the different signs that appear together by a negative sign:  

different sign e1605974365689

  e.g.   +8  + ( 4) =   8     4    =   4  

  e.g.  +4     ( + 1)   =   4  1

In other words,    \( \scriptsize – \; \times \; + = \;- \\ \scriptsize + \; \times \; – \; =\; – \)

Example

Find the values of the following:

i. (+5)    +   (+4)

ii. (+10)  –  (+5)

iii. (+12)  +  (-7)

iv. (+6)  –  (-5) 

v. (-9)  –  (-6)

Solution

i. (+5)   +  (+4)

\( \scriptsize + \; \times \; + \; = + \)

= 5  +  4  

=  9

 Note: +5   =  5

ii. (+10)  –  (+5)

\( \scriptsize – \; \times \; + \; = \; – \)

= 10   –  5 

=  5

iii. (+12)  +  (-7)

+  x   –  =   –

=    12  –  7 

=  5

iv. (+6)  –  (-5) 

\( \scriptsize – \; \times \; – \; = \; + \)

= 6   +    5    

=  11

v. (-9)   – (-6)

\( \scriptsize – \; \times \; – \; = \; + \)

=   -9   +  6  

=   -3

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