When we add, we move right on the number line.
When we subtract, we move left on the number line
To evaluate –3 + 2 , we start at –3 and move 2 places to the right
The answer is –1
To evaluate –3 – 2 , we start at –3 and move 2 places to the left
The answer is –5
How to add integers and subtract integers using the number line?
How to think about adding and subtracting integers on a number line?
Using the number line to add or subtract integers may be quite tedious. A quicker method would be to use the following rules:
Rule 1 :
The sum of two or more positive integers is a positive integer.
The sum of two or more negative integers is a negative integer.
(+7) + (+ 4) = + 11
(– 8) + (– 9) = – 17
Rule 2 :
To find the sum of a positive and a negative integer:
Subtract the two numbers (ignore the signs) and then keep the sign of the larger integer.
(– 9) + (+ 7) = – 2
(– 3) + (+ 5) = + 2
Rule 3 :
The sum of an integer and its opposite is equal to zero
(– 9) + (+ 9) = 0
(– 3) + (+ 3) = 0
How to use the rules to add integers?
To subtract integers, we can rewrite the subtraction problem as an addition problem. Instead of subtracting, we add the opposite.
Subtracting a positive is the same as adding a negative. 3 − (4) = 3 + (−4)
Subtracting a negative is the same as adding a positive. 3 − (− 4) = 3 + 4
We then follow the rules for adding integers.
Basic rules for subtracting integers and provides examples
Each subtraction problem is rewritten as an addition problem.
Subtracting Integers using Rules
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