Download E-Lesson

Adding and Subtracting
Integers
Objectives
By the end of this unit, the
seventh grade will
successfully
• Add negative and
positive integers
• Subtract negative and
positive integers
Quick Review
• A positive number is greater than zero
• A negative number is less than zero
• Opposite numbers are numbers that are
the same distance from zero in the
opposite direction (ex. 5 & -5)
• Absolute value is the distance from zero
-
+
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
Adding Integers: Same Signs
If the sign of the numbers are same, then
• Add the absolute values of the numbers
5
+
(
10)
• Keep the sign of the numbers
5 + 10 = 15
-15
Adding Integers ( Same Signs)
More Examples
Example 1:
Example 2:
11+ 6
-14 + (- 4)
11 + 6 = 17
14 + 4 = 18
= 17
= -18
If you don’t see a
negative or positive
sign in front of a
number, then it is
positive.
Both signs are
negative so the
answer will have the
negative sign.
Adding Integers: Different Signs
If the signs of the integers are different,
then . . .
• Subtract the absolute values of the integers
• Keep the sign of the number with higher
- 5 + 15
absolute value
15 - 5 = 10
10
15 has the higher
absolute value, so
the answer will also
be positive
Adding Integers ( Different Signs)
More Examples
Example 1:
Example 2:
-18 + 6
20 + (-14)
18 - 6 = 12
20 - 14 = 6
= -12
= 6
The answer is
negative, because 18
has the higher
absolute value.
The answer is
positive, because 20
has the higher
absolute value.
Practice: Adding Integers
Write down the answers on a separate sheet of paper.
Check your answers by clicking the check below.
1.) -5 + (-12)2.) -17 + (-5)
3.) 16 + (-6)
5.) -23 + 4
4.) 18 + 5
Practice: Adding Integers
Answers
1.) -5 + (-12)
= - 17
2.) -17 + (-5)
Same signs so add and
keep negative sign
3.) 16 + (-6)
= 10
Different signs so subtract and
keep positive sign because 16 > 6
= - 22
Same signs so add and
keep negative sign
4.) 18 + 5
= 23
Same signs so add and
keep positive sign
5.) -23 + 4
= -19
Different signs so subtract and
keep negative sign because 23 > 4
Continue
Subtracting Integers
• Rewrite the subtraction problem into an
addition problem
• Add the opposite of the second number
• Follow -the
12 rules
- 8 of addition
- 12 + (-8)
1. Rewrite as
addition problem
= - 20
2. The opposite of
positive 8 is -8.
3. Follow addition rules- same sign
you add and keep negative sign
Subtracting Integers
More Examples
Example 1:
Example 2:
-11 – (- 3)
28 – 36
1. Rewrite as
-11 +
addition problem
= -8
2. The opposite of
positive -3 is 3
3. Follow addition rulesdifferent sign you subtract
and keep negative sign
3
28 + (- 36)
= -8
1. Rewrite as
addition problem
2. The opposite of
positive 36 is -36
3. Follow addition rulesdifferent sign you subtract
and keep negative sign
Practice: Subtracting Integers
Write down the answers on a separate sheet of paper.
Check your answers by clicking the check below.
1.) -7 – (-5)
2.) -8 – 3
3.) 16 – 25
4.) 18 – (-11)
5.) -23 – 15
Practice: Subtracting Integers
Answers
1.) -7 – (-5)
2.) -8 – 3 = -11
= -7 + 5
= -8 + (-3)
= -2
= -11
3.) 16 – 25 = -9
= 16 + (-25)
= -9
4.) 18 – (-11) = 29
= 18 + 11
= 29
5.) -23 – 15 = -38
= -23 + (-15)
= -38
Continue
Jingle
Sing this jingle to the melody of “Row, Row, Row, Your Boat” to help
you memorize the rules of adding and subtracting integers. Click the
sound icon.
Same sign, add and keep,
Different sign, subtract.
Take the sign of the higher number,
Then it’ll be exact!
Change the minus to a plus,
Change the sign of next,
And all you do is add them up as if it were a plus.
© Microsoft Office 2003
Continue
Assessment
Question 1
Click on the correct answer.
1.) -15 + (-13)
a) -2
b) 28
c) -28
d) 2
Correct!
Congratulations!
You got the correct
answer!
-15 + (-13) is -28
© Microsoft Office 2003
Continue to Question 2
Oops!
I’m sorry that was incorrect.
Remember, same signs you
add and keep the sign. In this
case the signs are negative, so
the answer is negative.
-15 + ( - 13) is - 28
Continue to Question 2
Assessment
Question 2
Click on the correct answer.
2.) -11 - (-5)
a) -6
b) 6
c) -16
d) 16
Correct!
Congratulations!
You got the correct
answer!
-11 - (-5) is -6
© Microsoft Office 2003
Continue to Question 3
Oops!
I’m sorry that was incorrect. Remember,
change into an addition problem. Add the
opposite. The signs are different so you
subtract and keep the sign of the higher
number.
-11 - (-5)
= -11 + 5
= -6
Continue to Question 3
Assessment
Question 3
Click on the correct answer.
3.) 24 - 36
a) 12
b) -12
c) -60
d) 60
Correct!
Congratulations!
You got the correct
answer!
24 – 36 is -12
© Microsoft Office 2003
Continue to Question 4
Oops!
I’m sorry that was incorrect. Remember,
change into an addition problem. Add the
opposite. The signs are different so you
subtract and keep the sign of the higher
number.
24 – 36
24 + (-36)
= -12
Continue to Question 4
Assessment
Question 4
Click on the correct answer.
3.) 18 + (-17)
a) -1
b) 1
c) 35
d) -35
Correct!
Congratulations!
You got the correct
answer!
18 + (-17) is 1
© Microsoft Office 2003
Continue to Question 5
Oops!
I’m sorry that was incorrect.
Remember, different signs you
subtract and keep the sign of
the higher number.
18 + (-17) is 1
Continue to Question 5
Assessment
Question 5
Click on the correct answer.
5.) -16 - 9
a) 7
b) -7
c) 15
d) -15
Correct!
Congratulations!
You got the correct
answer!
-16 – 9 is -25
© Microsoft Office 2003
Continue
Oops!
I’m sorry that was incorrect. Remember,
change into an addition problem. Add the
opposite. The signs are the same so you
add and keep the sign.
-16 – 9
-16 + (-9)
= -25
Continue
Extra Practice
Complete the following problems on a separate
sheet of paper.
1.) -22 + 11
6.) -6 + 1
2.) 53 + (-53)
7.) -6 + 18
3.) 2 – 5
8.) 16 – (-34)
4.) -6 – (-4)
9.) 49 + (-39)
5.) -8 – 5
10.) 9 – 42
Continue
Congratulations
You have just completed the program! Remember to sing
the song and continue to practice. If you have extra time,
go on the following websites for more practice.
http://www.aaamath.com/g65-add-3negative.html
http://www.aaamath.com/g65-sub-negative.html
http://www.aaamath.com/g65-compareintegers.html
© Microsoft Office 2003