Transcript Add/Subtract Unlike Fractions

Add & Subtract
Unlike Fractions
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7 Grade
Math
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Lesson Objective:
Students will add and subtract
fractions with unlike
denominators.
Vocabulary
0011 0010 1010 1101 0001 0100 1011
• Unlike Fractions
– Fractions with different denominators
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Steps
0011 0010 1010 1101 0001 0100 1011
1. Rename the fractions using the least
common denominator (LCD)
2. Add or subtract as with like fractions
3. If necessary, simplify the sum or
difference
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Add Unlike Fractions 1
0011 0010 1010 1101 0001 0100 1011
• Add. Write in simplest form.
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1
LCD = 4

2
4
1x 2
1

2x2
4
2 1
2 1
3
 

4 4
4
4
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Add Unlike Fractions 2
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• Add. Write in simplest form.
9  1
    LCD = 10
10  2 
9  1x5 
 

10  2 x5 
9  5  9  ( 5) 4 2
   

or
10  10 
10
10 5
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Whiteboard Practice
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• Add. Write in simplest form.
5  4
    
6  9
2 5
  
3 6
1 3
 
6 8
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Subtract Unlike Fractions 1
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• Subtract. Write in simplest form.
2 1
LCD = 6

3 2
2 x 2 1x 3

3x 2 2 x 3
4 3 43 1
 

6 6
6
6
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Subtract Unlike Fractions 2
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• Subtract. Write in simplest form.
1  2
    LCD = 10
2  5
1x5  2 x 2 
 

2 x5  5 x 2 
5  4  5  ( 4 ) 9
   

10  10 
10
10
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Whiteboard Practice
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• Subtract. Write in simplest form.
3  1
   
8  4
3 1
 
4 3
7 5
 
12 6
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Real World Example
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• Cassandra cuts 5/16 inch off the top of a
photo and 3/8 inch off the bottom. How
much shorter is the total height of the photo
now? 5 3

LCD = 16
16 8
5 3x 2

16 8 x 2
5 6
5  6 11
 
 inch
16 16
16 16
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Whiteboard Practice
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• A bucket was 7/8 fill with soapy water. After
washing the car, the bucket was only ¼ full.
What part of the water was used?
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