Summary MTH1W (Ontario Grade 9 Math ) – Integers Made Easy (Add, Subtract, Multiply & Divide)

MTH1W – Integers (Number Sense)


Integers
-​ Set of whole numbers that include all positive/negative numbers, and zero.
-​ No fractions or decimals
​ Integers (Z): {..., -4, -3, -2, -1, 0, 1, 2, 3, 4…}
-​ Visualised on number line


-​ Extends infinitely on both positive and negative ends
-​ Useful to determine which integers are bigger or smaller and by how much

Real-life situations involving integers
-​ Temperature​ ​ ​ +5°C (above zero), −10°C (below zero)
-​ Money (bank accounts) ​ +$200 (credit), -$50 (debt)
-​ Game/Sport Scores​ ​ +3 points, -1 points loss

Addition and Subtraction
-​ Adding positive integers → move right
-​ Adding negative integers → move left
-​ Subtracting positive integers → move left
-​ Subtracting negative integers → move right
-​ Note if + is beside - then it becomes -, if - is beside - then it becomes +
-​ i.e. 5 + (- 6) = -1 → 5 - 6 = -1​ 5 - (-6) = 11 → 5 + 6 = 11
Example
Addition



-5 + 3 = -2​ ​ ​ ​ 3 + (-5) = -2
Subtraction



-3 - (-5) = 2​ ​ ​ ​ 6-4=2

Working Examples
1)​ Evaluate the following with number line
a)​ -3 - 2 = -5 b)​ 7 + (-3) = 4




c)​ 9 + 5 = 14 d)​ 5 - 8 = -3



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