To add and subtract negative numbers we can use a number line.
When we add we move to the right and when we subtract we move to the left.
Example 1:
-3 + 5
The first number is the starting point. We start at -3.
We are adding so we are moving to the right.
We move 5 spaces to the right.
-3 + 5 = 2
Example 2:
-2 - 6
The first number is the starting point. We start at -2.
We are subtracting so we are moving to the left.
We move 6 spaces to the left.
-2 - 6 = -8
Example 3:
-4 + -5
The first number is the starting point. We start at -4.
We are adding so we are moving to the right.
We move -5 spaces to the right (this means we move 5 spaces to the left)
-4 + -5 = -9
Example 4:
2 - -5
The first number is the starting point. We start at 2.
We are subtracting so we are moving to the left.
We move -5 spaces to the left (this means we move 5 spaces to the right)
2 - -5 = 7
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Multiplying and Dividing Negative Numbers
When we multiply negative numbers we use the rules:**
Positive × Positive = Positive
Positive × Negative = Negative
Negative × Positive = Negative
Negative × Negative = Positive**
The rules for multiplying and dividing negative numbers are the same:**
Positive ÷ Positive = Positive
Positive ÷ Negative = Negative
Negative ÷ Positive = Negative
Negative ÷ Negative = Positive**
Example 5:
-6 × 2
6 × 2 = 12
Negative × Positive = Negative
-6 × 2 = -12
Example 6:
7 × -5
7 × 5 = 35
Positive × Negative = Negative
7 × -5 = -35
Example 7:
-9 × -4
9 × 4 = 36
Negative × Negative = Positive.
-9 × -4 = 36
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