Chapter 02 Section 05

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Chapter 02 Section 05

• Adding and Subtracting Rational Numbers

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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
OBJECTIVES
To add and subtract rational numbers and to
simplify expressions that contain rational
numbers.
This section is simple. You use the rules from
section 2-3 about adding and subtracting
integers. Only in this section, you will need to
find common denominators before adding and
subtracting. Your calculator will be a big help
for you in this section. On the next slide is a
review of the rules of adding and
subtracting. After that, its just examples.
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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
To add or subtract integers and rational numbers,
follow these rules 1) If the statement is a
subtract statement, change it to an add statement
by adding the opposite of what is being
subtracted. Example 2 (-4) gt 2 4 2) If
the two terms being added have the same sign,
combine their absolute values (strengths) and
keep the sign. Example 2 8 10 and -2
(-8) -10 3) If the two terms being added have
different signs, subtract their absolute values
(strengths) and keep the sign of the
stronger. Example -2 8 6 and 2 (-8)
-6 You must have these rules committed to memory
as of right NOW!!!
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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
EX1ß
EXAMPLE 1a Find each sum. a. b. -1.34
(-0.458) c.
Rewrite mixed numbers as improper fractions.
Rewrite mixed numbers as improper fractions.
Line up the decimal places.
Get a common denominator.
Get a common denominator.
-1.798
Add the numbers strengths and keep the sign.
Add.
Add.
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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
EXAMPLE 1ß Find each sum. a. b.
-8.007 (-5.755)
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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
EX2ß
EXAMPLE 2a Find each difference. a.
b. -6.24 8.52
Get a common denominator.
Remember subtracting is the same as adding the
additive inverse.
-6.24 (-8.52)
Negative negative yields a positive.
Line up the decimals.
Add strengths and keep sign.
Subtract the strengths and keep the sign of the
stronger number.
-14.76
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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
EXAMPLE 2ß Find each difference. a. b.
c. 6.32 (-3.42)
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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
EX3ß
EXAMPLE 3a a. Evaluate p - 3.5 if p
2.8. b. Evaluate if
(2.8) - 3.5
Plug in 2.8 for p.
-0.7
Subtract strengths and take the sign of the
stronger.
Plug in the value of x.
Get a common denominator.
Subtract strengths and take sign of the stronger.
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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
EXAMPLE 3ß Evaluate. a. p 7.1 if p
5.2 b. if
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2-5 ADDING AND SUBTRACTING RATIONAL NUMBERS
HOMEWORK
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