Addition and Subtraction
It should be noted that:
a)
+ - =
-
b)
- + =
-
c)
- - =
+
d)
+ + =
+
As a student, please try: (
For this questions, please draw a number line as the one shown above from -14 to +14 )
i) 4 + 8
ii) -4 + 8
iii) 4-(-8)
iv) 4-8
(
Check solution below)
i) 4 + 8
This can be represented as: +4 + (+8).
Using a number line, start at position 0. Move 4 steps to the right and further 8 steps to the right. What do you get?
If your answer is +12, you are correct.
ii) -4 + 8 is the same as -4 + (+8)
On the number line, start at position 0, move 4 to the left and then move 8 steps to the right.
Your answer should be +4 or simply, 4
iii) 4 - (-8) is the same as +4 - (-8).
Remember, - - = +, hence the above problem is the same as 4 + 8
On the number line, start at position 0. Move 4 steps to the right and a further 8 steps to the right.
Your answer should be +12 or simply, 12
iii) 4 - 8 is the same as +4 - (+8).
Remember, - + = -, hence the above problem is the same as 4 - 8
On the number line, start at position 0. Move 4 steps to the right and a then 8 steps to the left.
Your answer should be -4
Multiplication and Division
Rules of Multiplication and Division:
Positive x
positive =
positive
Positive x
negative =
negative
negative x
negative =
positive
negative x
positive =
negative
Positive ÷
positive =
positive
Positive ÷
negative =
negative
negative ÷
negative =
positive
Order of Operations
Remember
BODMAS? This rule is followed in the order of operations.
BODMAS stands for
Bracket,
Of,
Division,
Multiplication,
Addition,
Subtraction
Example: Solve 4 x 2(10-4) + 9 ÷ 3 - 10
Using BODMAS
= 4 x 2(10 - 4) + 9 ÷ 3 - 10
= 4 x 2(6) + 9 ÷ 3 - 10
= 4 x 12 + 9 ÷ 3 - 10
= 4 x 12 + 3 - 10
= 48 + 3 - 10
= 51- 10
= 41
