Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8.


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Quarter 4

Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8.
Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8.
Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8.
Understand subtraction as an unknown-addend problem. For example, subtract 10 - 8 by finding the number that makes 10 when added to 8.

Enduring Understanding

Mathematical operations are used in solving problems in which a new value is produced from one or more values.
Algebraic thinking involves choosing, combining, and applying effective strategies for answering quantitative questions.number_balance.jpg

Essential Questions

In what ways can operations affect numbers?
How can different strategies be helpful when solving a problem?

Vocabulary (online dictionary, HCPSS Vocabulary Cards)

Addition, add, subtraction, subtract, addend

About the Math

It is important for students to share, discuss and compare their strategies as a class. Students will use the relationship between addition and subtraction as a strategy to solve unknown-addend problems. Students naturally connect counting on to solving subtraction problems. For the problem “15 – 7 = ?” they think about the number they have to add to 7 to get to 15. First graders should be working with sums and differences less than or equal to 20 using the numbers 0 to 20.

Provide multiple opportunities for students to study the relationship between addition and subtraction in a variety of ways, including games, modeling and real-world situations. Students need to understand that addition and subtraction are related, and that subtraction can be used to solve problems where the addend is unknown.

Illustrative Mathematics Project Task: Fact Families


Rich Tasks for Multiple Means of Engagement, Expression, and Representation (UDL)

Missing-Part Subtraction:
A fixed number of counters is placed on a mat making sure that both students know the quantity (the total). One child separates the counters into twp parts while the other child hides his or her eyes. The first child covers one of the two parts with a sheet of tagboard, revealing only the other part. The second child says the subtraction sentence. For example, "Nine minus four (the visible part) is five (the covered part). The covered part can be revealed if necessary for the child to say how many there are. Both the subtraction equation and the addition equation can then be written.

Grab-Bag Subtraction:
Materials: a collection of cubes and 1 paper bag per pair of students.
Instructions:
  1. Select a number of objects for the students to work with. Player 1 fills the bag with that number of cubes.
  2. Player 2 reaches in and removes some cubes, showing player 1 how many he or she has taken.
  3. Both players predict how many cubes are still in the bag and then check their predictions.
  4. Each player records the number sentence in his or her journal ( ex. 15 - 7 = 8).

Journal Prompt:

Emily had to find the missing number in this number sentence:
17 - __ = 9
Find the missing number. Describe how you found the answer. Or draw a picture that show how you found the answer.
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Print Resources:

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Math Intervention-Building Number Power
PreK-2 (115--117)


Web Resources:

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Games and Centers
Lessons
Student Resources
Video Segments
Printable
Ten Frame Subtraction

Center Ideas
Subtraction Games

Online GamesMinus MissionTen FrameFive FrameSomething's Missing Missing

Lesson Plans
Missing Part Subtraction
Try For Five
Fact Family Fun
Macaroni Math
Finding Fact Families

Lesson Seeds
Ten in the Bag
Flash a Ten Frame
A Sense of Ten

Printable Tools
Function Table Template
Magic Pot Workmat
The Number Crew: After LIfeboat Practice
Think Addition (audio file)
Missing Addend Grab Bag (Michelle Glenn, CLES)





Questions/Comments:

Contact John SanGiovanni at jsangiovanni@hcpss.org.


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Howard County Public Schools Office of Elementary Mathematics Curricular Projects has licensed this product under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.