Integers
Adding—Same Signs
Two Negative Numbers
Two Positive Numbers
Ex.) -4 + -3
Ex.) 2 + 9
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Just add the numbers, you’ve
been doing this since 2nd Grade.
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Just add the numbers, and keep
the negative sign.
-4 + -3 = -7
2 + 9 = 11
• Illustration
• Illustration
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Adding—Different Signs
One number is Positive,
One number is negative
Ex.) 6 + -5
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Subtract the Absolute Value of the
Numbers, and take the sign of the
larger Absolute Value
6 + -5 = 1
Follow the steps:
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Abs. Value of 6 = 6
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Abs. Value of -5 = 5
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6-5=1
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6 is larger than 5, so the answer
is positive, because the 6 is
positive
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+
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Remember:
+
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A + plus a – cancel
each other out.
+
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Illustration
+ + - =0
+
More Examples
Ex.) -5 + 3
(Different Signs…)
Ex.) -3 + -7
(Same Signs…)
Visual
Visual
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Integer Addition Strategies
• Opposite Pairs
+
-
• A + and a – cancel each other out.
• Have $/Owe $
• Think of Positive Numbers as having $, and think of Negative Numbers as
owing someone $.
www.wpclipart.com/money/money_bag_green.png
• Number Line Walk
• Put Sammie on the number line above the 1st #, then “walk” Sammie the
number of space of the 2nd #. If the 2nd # is positive, walk to the RIGHT, if it
is negative, walk to the LEFT.
•
dhardhar.files.wordpress.com/2009/08/cartoon-...
Subtracting
• You have been
subtracting “Positive
Integers” since 2nd grade
Ex.) 12 - 8 =
Ex.) 9 – 7 =
Ex.) 53 – 22 =
• KFC—Keep, Flip, Change
Keep—the sign of the 1st Number
Flip—the operation + becomes –
Change—the sign of the 2nd Number
So,…
• BUT…from now on…we
are going to change
Subtraction to Addition by
KFC
Ex.) 12 – 8
becomes 12 + -8
??What do you notice about the answer??
Subtracting—use KFC
Ex.) 7 – 11=
(KFC…7 + -11=) now use an
addition strategy to solve.
Ex.) -7 – 12=
Ex.) 8 – 16=
Ex.) -4 – 1=
Ex.) 3 – 12=
Ex.) 5 – -2=
Ex.) -8 – -6=
Multiplying & Dividing
• The Triangle Trick
Ex.) 9 × -8 =
+
Ex.) -28 ÷ 7=
-
1. × or ÷ the
numbers.
2. Cover up the Signs of
the numbers.
3. The sign left over, is the
sign of the answer.
Ex.) -3 × -11 =
Ex.) -36 ÷ -6=
-