Adding and Subtracting Integers

1
Adding and Subtracting Integers Using Counters
June Posten EDUC 570 Summer 2007
3 -1
2
Integer Components
3
What are integers?

• The whole numbers and their opposites , -3,
  -2, -1, 0, 1, 2, 3,

• Negative numbers, zero, and positive numbers

1
- 1
4
Where Do We See Integers?
Stock Market
Temperature
Wind Chill Factor
Money (Debit/Credit)
5
Where Do We See Integers?
Football (gains/loss)
Elevators (up/down, above below ground
classroomclipart.com
Board games (forward and backward)
Weight (gain/loss)
6
Where Do We See Integers?
Elevation

• Mount McKinley
• Highest point in the U.S.
• 20,320 feet above sea level
• Expressed as 20,320 feet
• Sea level is zero feet

http//boston.k12.ma.us/teach/technology/select/gr
ade7/units
7
Where Do We See Integers?
Elevation

• Death Valley
• Lowest point in the U.S.
• Elevation is 282 feet below sea level
• Expressed as -282 feet

http//boston.k12.ma.us/teach/technology/select/gr
ade7/units
8
Using Counters to Add Subtract Integers
Yellow counters are positive ()

-
Red counters are negative (-)
0

-

1 red and 1 yellow ZERO (1) (-1) 0
You can add zero to anything and the value stays
the same 6 0 6 -3 0 -3
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Adding Positive Integers











5
3
2
Three plus two
Answer 3 2 5
10
Adding a Negative Integer
Equals zero


-




-

3 (-1)
3
-1
Three plus a negative one
Answer 3 (-1) 2
11
Subtracting a Positive Integer




4
- 1
Four minus a positive one
Answer 4 1 3
12
Subtracting a Negative Integer
No negatives to take away!


Add zero ( )

-
-

Now subtract the -1
2
- (-1)
Two minus a negative one
Answer 2 (-1) 3
13
Try some problems on your own

• 4 2
• 4 2
• 8 3
• 7 (-2)

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