Decomposing and Composting Fractions
4.NF.B.3b
Understand a fraction a/b with a>1 as a sum of fractions 1/b. Decompose a fraction into
a sum of fractions with the same denominator in more than one way, recording each
decomposition by an equation. Justify decompositions, e.g. by using a visual fraction model
Math Practices:
 MP1 – Make sense of problems and persevering in solving them
 MP3 – Construct viable arguments and critique the reason of others
 MP4 – Model with mathematics
Focus: How can we use addition to represent a fraction in a
variety of ways?
Engage: Read math literature: The Wishing Club by Donna
Jo Napoli. Preview the cover and encourage kids to notice
how the characters encounter fraction related problems in the
story. Make predictions based on cover and title
Connect: What are some different ways you can write 10 as a
sum?
___________________________________________________________________
Pose the Problem: Valentine has 7/8 of a pound of oatmeal to put into three bowls. How
much could she put into each bowl, if the amount of oatmeal did not have to be the same in
each bowl? Write your answer in an addition sentence that looks like…
7/8 = ____ + ____ + ____
Decomposing and Composting Fractions
Direct Instruction:
1. Review vocabulary (fractions, numerator, denominator, like denominators)
2. Introduce new vocabulary (decompose, compose, variety of ways)
3. Read word problem: Charlize has a beautiful garden. She wants to leave 1/6 of
her garden empty. What are some different ways she can plant the rest of her garden?
5/6 planted
1/6 empty
4. Questioning:
How many equal parts is the garden divided up into? 6
What is the name of each part? 1/6
How much of the garden will be planted? 5/6
One Way
Another Way
She could plant 4 sections blue flowers and
She could plant 1 section green beans, 1
1 section strawberries
section red peppers, 1 section strawberries,
and 2sections blue flowers
5/6= 4/6 + 1/6
5/6= 1/6 + 1/6 + 1/6 + 2/6
Guided Practice:
Review how to use models such as fraction strips or drawing a picture to show a
fraction as part of a whole.
1. 3/5 =
3/5=
2. 1 3/4=
1 3/4=
Decomposing and Composting Fractions
3. 8/10=
8/10=
4. 1 2/3=
1 2/3=
Independent Practice
Review criteria and rubric
Write your own Wishing Story math problem. See teacher created worksheet.
Assessment
Students work independently to complete the Quick Check Assessment
Close
"In today's lesson, you learned to write a fraction as a sum of fractions in more than
one way. You also applied math concepts and skills to real-world problems"
Extension
Technology integration:
Brainpop
https://www.brainpop.com/
Decomposing and Composting Fractions
Brainpop Jr.
https://jr.brainpop.com/
ST Math
http://web.stmath.com/
Decomposing and Composting Fractions
Homework
http://www.mathplayground.com/ASB_Speedway.html
Students will post a screenshot of their activity and name for proof and submit through
Edmodo, or Class Dojo for credit