Transcript 3rd_MA_NS_3.2_SUBTRACT_FRACTION_COMMON_DENOM

Name __________________________
Learning Objective
Today, we will subtract fractions with a common denominator.
CFU
What are we going to do today?
What are we going to subtract?
Activate (or provide) Prior Knowledge
What is the difference1?
1Answer
1.
to the subtraction problem.
4 parts
–
2 parts
=

2 parts
2
4
2.
3 parts
–
2 parts
=

1 part
1
4
CFU
Teacher completes problem #1, students complete problem #2. Students, you already know how to use pictures to subtract
fractions. Today, we are going to just use numbers to subtract fractions with a common denominator.
DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Concept Development
A fraction represents a specific part of a whole.
• The top number of a fraction is called the numerator.
• The bottom number of a fraction is called the denominator.
1
2
When subtracting fractions, both fractions must have the same number in the denominator, or a
common denominator.
• Subtract fractions by subtracting the numerators.
• The denominator does not change.
Examples:
3
1
4
4
3 1
2
4
4
CFU
Which fraction has 3 in the numerator and 8 in the
denominator? How do you know?
A.
3
A.
8
4
3
5
5
B.
2
2
5
3
Which picture shows one-third? How do you know?
2
1
4
2
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
3
Which subtraction has common denominators? How do
you know?
After subtracting the fractions, draw a picture
representing your answer to see if there are any
equivalent fractions with lower numbers.
DataWORKS Educational Research
B.
8
A.
B.
In your own words, what is the numerator?
The numerator is ____________________.
In your own words, what is the denominator?
The denominator is ____________________.
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Importance
When subtracting fractions, both fractions must have the same
number in the denominator, or a common denominator.
• Subtract fractions by subtracting the numerators.
• The denominator does not change.
Numerator
Denominator
It is important to subtract fractions with a common denominator
because:
1. subtracting fractions with a common denominator will help you measure
ingredients while cooking.
2
cups of flour. He knows that he
3
1
will need to measure out a cup and then of a cup twice.
3
James is baking a cake and it calls for 1
2. subtracting fractions with a common denominator will help you do
well on tests.
CFU
Does anyone else have another reason why it is important to subtract fractions with a common denominator? (pair-share) Why is it
important to subtract fractions with a common denominator? You may give me one of my reasons or one of your own. Which reason is
more important to you? Why?
DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Skill Development/Guided Practice
When subtracting fractions, both fractions must have the same number in the
denominator, or a common denominator.
Subtract fractions.
Numerator
Denominator
Step #1: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #2: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #3: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #4: Read the subtraction problem with the difference.
1. 5 2
3
 
6 6
6
Does not go
in evenly.
2. 3 1
2
 
6 6
6



3
1
2
Does not go
in evenly.

1
3
2
CFU
How did I know how to write the subtraction problem? How did I know if the fractions had a common denominator? How did I know what
to do with the denominator in the answer? How did I know which numbers to subtract? How did I know how to shade the figures? How did
I know how to check for equal fractions? How did you know how to write the subtraction problem? How did you know if the fractions had a
common denominator? How did you know what to do with the denominator in the answer? How did you know which numbers to subtract?
How did you know how to shade the figures? How did you know how to check for equal fractions?
3rd Grade Number Sense 3.2 (2Q)
DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Skill Development/Guided Practice (continued)
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Subtract fractions.
Step #1: Set up the subtraction problem by reading the question.
Step #2: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #3: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #4: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #5: Read the subtraction problem with the difference.
3. A pizza was divided into eight slices. Nathan ate 3of
8
2 the pizza. How much more
the pizza. Janelle ate
of
8
pizza did Nathan eat?
3
8

2
8

4. A pizza was divided into eight slices. David ate 4 of
8
the pizza. Daisy ate 1 of the pizza. How much more
8
pizza did David eat?
1
4
8
8


4
2
Denominator

1
8

3
8


4
2
CFU
How did I know how to write the subtraction problem? How did I know if the fractions had a common denominator? How did I know what
to do with the denominator in the answer? How did I know which numbers to subtract? How did I know how to shade the figures? How did
I know how to check for equal fractions? How did you know how to write the subtraction problem? How did you know if the fractions had a
common denominator? How did you know what to do with the denominator in the answer? How did you know which numbers to subtract?
How did you know how to shade the figures? How did you know how to check for equivalent answers?
DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Closure
1. In your own words, what is the numerator?
2. In your own words, what is the denominator?
3. Subtract the fractions below.
4. What did you learn today about subtracting fractions with a common denominator? Why is that important
to you? (pair-share)
Step #1: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #2: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #3: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #4: Read the subtraction problem with the difference.
1.
Numerator
Denominator
2
4 2
 
4 4
4

DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
1
2
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Independent Practice
Name________________________
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Denominator
Subtract fractions.
Step #1: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #2: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #3: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #4: Read the subtraction problem with the difference.
1. 9
4
5


10 10 10
2. 7
5
2


10 10 10


DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
2
5
2


5
1
2
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Independent Practice (continued)
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Subtract fractions.
Step #1: Set up the subtraction problem by reading the question.
Step #2: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #3: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #4: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #5: Read the subtraction problem with the difference.
3. A pie was divided into nine slices. Julie ate 4 of the
9
1
pie. Phillip ate
of the pie. How much more pie did
9
Julie eat?
4
9

1
9

3
9
DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
4. A pie was divided into nine slices. Greg ate 7 of the
9
1
pie. Sara ate
of the pie. How much more pie did
9
Greg eat?
7
9

1
3
Denominator

1
9

6
9

2
3
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Periodic Review 1
Name________________________
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Denominator
Subtract fractions.
Step #1: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #2: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #3: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #4: Read the subtraction problem with the difference.
1. 3
2. 6
2
1
 
4 4
4
6

1

4
2

6
6

2

DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
2
3
2
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Periodic Review 1 (continued)
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Denominator
Subtract fractions.
Step #1: Set up the subtraction problem by reading the question.
Step #2: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #3: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #4: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #5: Read the subtraction problem with the difference.
3. A pizza was divided into eight slices. Jose ate 4 of
8
2
the pizza. Jessica ate
of the pizza. How much more
8
pizza did Jose eat?
4
8

2
8

7
2
8
10


DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
4. A pineapple was cut into ten slices. Marcos ate 7
10
1
of the pineapple. Rose ate
of the pineapple. How
10
much more pineapple did Marcos eat?

1
10

6
10
1
4

2

3
5
2
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Periodic Review 2
Name________________________
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Denominator
Subtract fractions.
Step #1: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #2: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #3: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #4: Read the subtraction problem with the difference.
1. 3
1
2
 
5 5
5
2. 8
9

2
6

9
9

DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
3
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Periodic Review 2 (continued)
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Denominator
Subtract fractions.
Step #1: Set up the subtraction problem by reading the question.
Step #2: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #3: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #4: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #5: Read the subtraction problem with the difference.
6 of the
3. A pie was divided into ten slices. Ken ate
10
4
pie. Jackson ate
of the pie. How much more pie
10
did Ken eat?
6
10

4
10

3
4. An orange was cut into four slices. Ray ate
of the
4
orange. Kristy ate 1 of the orange. How much more
4
orange did Ray eat?
2
3
10
4


DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
1
5

1
4

2
4
 1
2
2
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Periodic Review 3
Name________________________
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Denominator
Subtract fractions.
Step #1: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #2: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #3: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #4: Read the subtraction problem with the difference.
1. 9
7
2


10 10 10
2. 8
9


DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]

3
5

9
9

5
1
3
2
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.
Periodic Review 3 (continued)
When subtracting fractions, both fractions must have the same number in the denominator, or a common
denominator.
Numerator
Subtract fractions.
Step #1: Set up the subtraction problem by reading the question.
Step #2: Read the subtraction problem. Make sure both fractions have a common denominator.
Step #3: Find the difference of the fractions.
a. Denominator: Remains the same.
b. Numerator: Subtract the numerators of the fractions.
c. Represent the difference by shading in the figure below.
Step #4: Determine if the difference can be shown by an equal fraction using lower numbers.
a. Shade in the remaining figures below with the same amount of squares.
Step #5: Read the subtraction problem with the difference.
3 of the
3. An apple was cut into five slices. Joe ate
5
2
apple. Amanda ate of the apple. How much more
5
apple did Joe eat?
3
5

2
5

1
5
Denominator
4. A pizza was divided into six slices. Kim ate 4 of the
6
pizza. Taylor ate 1 of the pizza. How much more
6
pizza did Kim eat?
4
6

1
6

3
6

3
 1
2
DataWORKS Educational Research
(800) 495-1550 • www.dataworks-ed.com
©2011 All rights reserved.
Comments? [email protected]
3rd Grade Number Sense 3.2 (2Q)
Add and subtract simple fractions (e.g. determine
that ⅛+⅜ is the same as ½).
Lesson to be used by EDI-trained teachers only.