Download 1 Lesson 69--Negative Numbers/Absolute Value/Adding Signed

Lesson 69--Negative Numbers/Absolute Value/Adding Signed Numbers
Every postive number has an opposite to the left of zero on the number line.
­10
­9
­8 ­7
­6
­5 ­4
­3
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­1
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+4 means 4 units to the right of zero
-4 means 4 units to the left of zero
Numbers that have either a plus or minus sign are called _______________
_________________.
Each opposite is the same distance away from zero.
What do we call the distance away from zero?
Absolute Value--
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Let's look at adding signed numbers.
Ex: (+2) + (­3) ­5
We can use number lines to help us add signed numbers.
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­2
­3
­4
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Ex: Use arrows and a number line to add (­3) and (+5).
­5
­1
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­3
­4
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Ex: (+4) + (+2)
­5
­4
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­2
­1
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­3
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­1
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Ex: (­1) + (­3)
­5
­4
Now we aren't going to want to sketch a number line every time we add signed
numbers. There has to be some rules we can follow.
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1. To add numbers of the same numbers just add the numbers as usual and
carry the sign of the two numbers into your answer.
Ex: (2) + (3) =
Ex: (-2) + (-3) =
2. To add numbers of opposite signs just subtract the numbers and carry
the sign of the number that has the largest absolute value (or use the sign
of the number you have "more" of).
Ex: (­4) + (+3) =
Ex: (­2) + (+8) =
Ex: (45) + (­72) =
Ex: (­25) +(+63) =
Ex: (­4) + (+3) + (­5) + (7) =
On Your Own
Ex: Use a number line to add the following.
b. (-3) + (-4)
a. (-2) + (+4)
­5
­4
­3
­2
­1
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­10
­9
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­5 ­4
­3
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­1
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Ex: Add.
c. (-14) + (+2)
d. (41) + (-8)
e. (-4) + (-15)
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