Add and
Subtract Integers
Using Counters
Chapter 2
We can use the following colored
counters to model the sum &
Difference of integers with
different signs.
When you add a positive
integer (yellow counter)
and a negative integer
(red counter), the result
is 0.
1 + (-1) = 0
• One red and one yellow counter form a
zero pair.
Example 1 :
Evaluate : (-4) + (+3)
Solution :
Start with four negative counters to
represent -4 and three positive counters to
represent +3.
• Mark the zero pairs.
In the above figure, if you remove the three zero
pairs, the result will be one negative counter.
So, the answer is -1.
Therefore,
(-4) + (+3) = -1
Example 2 :
Evaluate :
(+5) - (+2)
Solution :
Write the given subtraction as
addition.
(+5) - (+ 2) = (+ 5) + (-2)
Start with five positive counters to represent +5 and
two negative counters to represent -2.
Mark zero pairs.
In the above figure, if you remove
two zero pairs, the result will be
three positive counters.
So, the answer is +3.
Therefore,
(+5) - (+2) = +3
Example 3 :
Find the sum of +4 and -7.
Solution :
Start with four positive counters to represent +4
and seven negative counters to represent -7.
Mark zero pairs.
In the above figure, if you remove
four zero pairs, the result will be
three negative counters.
So, the answer is -3.
Therefore,
(+4) + (-7) = -3
Evaluate: - 4 – (-3)
Then take away -3
So, you remove 3 red circle
Therefore, the answer is -1.
Evaluate: - 4 – (+3)
Remember, you need to
remove 3 yellows
Then we will add zero pair
Then remove the 3 yellows
Therefore, the answer is -7
Evaluate: +2 – (+5)
Remember, you need to
remove 5 yellows
Then we will add zero
pairs
Then remove the 5 yellows
Therefore, the answer is -3
Let’s Practice!
Find the sum of: (-5) + 2.
Let’s Practice!
Find the sum of: (-6) + (-3).
Let’s Practice!
Evaluate: 9 + (-3)
Let’s Practice!
Evaluate: -5 - (-2)
Let’s Practice!
Evaluate: -5 - (7)