Transcript Multiplying Fractions

Do Now 12/3/13
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Take out HW from last night.
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Text page 116, #1-19 odds
Copy HW in your planner.
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Text p. 134, #1-15 odds & #10
Benchmark Test Chapters 1, 2, 3, & 11 Wednesday
Homework
Text p. 116, #1-19 odds
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1) 34.41
3) 15.22
5) 32.64
7) 0.42
9) 12.29
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11) 28.1
13) 40
15) 7.5
17) 24.84
19) $21.92
Objective
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SWBAT review adding, subtracting, multiplying,
and dividing fractions and mixed numbers.
Mixed Numbers to Improper Fraction
40 + 1 = 41
8 x 5 = 40
1 41
8 
5 5
ADDITION &
SUBTRACTION
REVIEW
Section 3-5 “Adding and Subtracting Fractions”
Adding Fractions and Mixed Numbers with Common
Denominators
To ADD/SUBTRACT fractions with common
denominators:
1) Rewrite as improper fractions (if necessary)
2) Add/subtract their numerators.
3) Simplify if necessary.
2 3

7 7
2 3 5
 
7 7 7
5 1

6 6
4 2
 
6 3
Fractions with Different Denominators
To ADD or SUBTRACT fractions with different
denominators follow these steps:
1). Rewrite as improper fractions (if necessary)
2). Rewrite the fractions using a common denominator.
3). Add or subtract the numerators.
2 1

5 7
What is the common denominator?
5: 5, 10, 15, 20, 25, 30, 35, 40
7: 7, 14, 21, 28, 35, 42
2 ?

5 35
2  7 14

5  7 35 Equivalent
1 ?

7 35
1 5 5

7  5 35
14 5 19


35 35 35
fractions
Mixed Number Practice
1 3
4 1
4 8
1. Improper fractions
17 11

4 8
2. Common denominators
34 11

8 8
3. Subtract
numerators
23
7
 2
8
8
3
63 2
4
3
 6  3  (2)
4
“Opp-Opp”
Commutative property
3
 6  ( 2)  3
4
Simplify
3
83
4
Subtract numerators
 32 15

4
4
Subtract
numerators
 17
1

 4
4
4
MULTIPLICATION
REVIEW
Section 3-6, “Multiplying Fractions”
Multiplying Fractions
To multiply fractions:
1. Rewrite fractions as improper fractions (when necessary)
2. Multiply the numerators and denominators.
3. Simplify if necessary.
a c ac
 
b d bd
3 4 12
 
5 7 35
3  1
 2 3 
4  5
Mixed Number times
Mixed Number
Multiply
 11  16 
 
4 5
Rewrite as improper fractions and assign
negative to numerator.
4
 11 (16)
1 45
Divide (cancel) common factors
Multiply
 11  (4)
 44


1 5
5
Simplify
4
8
5
Word Problem
Who ran farther Sally Jo or Sally Sue?
Sally Jo ran 4 ½ times around a ½ mi. track.
Sally Sue ran 3 ¼ times around a 5/6mi. track
1 1
4  
2 2
9 1
 
2 2
9
1
2
4
4
1
6
2 2
4 24
1 5
13 5
65
17
3  
 
2
4 6
4 6
24
24
Sally Sue
ran farther!!
Word Problem
There are 36 students in your class. 2/3 of
them went on the class trip. How many students
went on the trip?
2
36 
3
Rewrite a
whole number
with a
denominator
of 1.
Whole Number times
Fraction
Multiply
36  2 
 
1 3
36  (2)
1 3 1
12
Divide (cancel) common
factors if possible
Multiply
12  2

1 1
24

1
Simplify
24
DIVISION
REVIEW
Section 3-7, “Dividing Fractions”
Dividing Fractions
To divide fractions:
1. Rewrite fractions as improper fractions (when necessary)
2. Write the reciprocal of the second fraction.
3. Multiply the numerators and denominators.
4. Simplify if necessary.
a c a d ad
   
b d b c bc
3 4 3 7 21 1
    1
5 7 5 4 20 20
RECIPROCAL –
two nonzero numbers whose product
is 1.
2 3 6
  1
3 2 6
4 7 28
  1
7 4 28
RECIPROCAL = MULTIPLICATIVE
INVERSE
7  4 
 
10  22 
Divide
7  22 
 
10  4 
Multiply by the RECIPROCAL
7   22 


10  4 
Assign negative sign to the numerator
-11
7  ( 22)
10  4
5
Divide (cancel) common factors
Multiply
7  (11)  77

5 4
20
17
3
20
A recipe that yields 2 loaves of bread requires
3½ cups of sugar. You have a bag of sugar
that contains 14¼ cups. How many cups of
sugar will be left in the bag if you make 8
loaves of bread?
8 loaves ÷ 2 loaves per batch = 4 batches
4 batches ∙ 3 ½ cups of sugar = 14 cups
14¼ cups – 14 cups for recipe = ¼ cup left over.
Benchmark Review
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Chapter 1 
Simplifying variable expressions
a + b; when ‘a’ = -12 and ‘b’ = 7
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Properties
Commutative 2+3=3+2
1 3 
1 3
1 3
 Associative 2   2     2    
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5
Identity  Distributive 
5

5 5
2+0=2
2(n + 4) = 2n + 8
5
5
Benchmark
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Chapter 2 
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Integers
Chapter 11 
Equations