Topic Two Understanding Subtraction

Pacing (Duration of Unit):

Desired Results

Transfer:
1. Makes sense of problems and persevere in solving them.
2. Reason abstractly and quantitatively.
3. Construct viable arguments and critique the reasoning of others.
4. Model with mathematics.
5. Use appropriate tools strategically.
6. Attend to precision.
7. Look for and make use of structure.
8. Look for and express regularity in repeated reasoning.
Established Goals:

  • 1.OA.1 Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
  • 1.OA.4 Understand subtraction as an unknown-addend problem. For example, subtract 10 – 8 by finding the number that makes 10 when added to 8.
  • 1.OA.6 Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use mental strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13).
  • 1.OA.7 Understand the meaning of the equal sign, and determine if equations involving addition and subtraction are true or false. For example, which of the following equations are true and which are false? 6 = 6, 7 = 8 – 1, 5 + 2 = 2 + 5, 4 + 1 = 5 + 2.

Student "I Can" Statements:

  • I can use strategies to solve addition word problems.
  • I can use strategies to sole subtraction word problems.
  • I can use an addition fact to help me answer a subtraction problem.
  • I can add facts within 20.
  • I can subtract facts within 20.
  • I know what an equal sign means.
  • I can tell if addition and subtraction equations are true or false.

Pre-Requisite Standards:

  • K.OA.1Represent addition and subtraction with objects, fingers, mental images, drawings, sounds (e.g., claps), acting out situations, verbal explanations, expressions, or equations.
  • K.OA.2 Solve addition and subtraction word problems, and add and subtract within 10, e.g., by using objects or drawings to represent the problem.
  • K.OA.4 Decompose numbers less than or equal to 10 into pairs in more than one way, e.g., by using objects or drawings, and record each decomposition by a drawing or equation (e.g., 5 = 2 + 3 and 5 = 4 + 1).

  • K.OA.5 Fluently add and subtract within 5.
Big Ideas:

Operation Meanings & Relationships
There are multiple interpretations of addition, subtraction, multiplication, and division of rational numbers and each operation is related to other operations.

Practices, Processes, and Proficiencies
Mathematics content and practices can be applied to solve problems.
Essential Questions:

What are ways to think about subtraction?
Students will know...

  • A missing part of a whole can be found when the whole and the other part are known.
  • A missing part of a whole is one interpretation of subtraction. Subtraction number sentences can be used to show a missing part subtraction situation.
  • Taking away parts from a whole is one interpretation of subtraction. Subtraction number sentences can be used to show taking-away subtraction situations.
  • Comparing two quantities to find out how much more/less one quantity is than the other is one interpretation of subtraction. Subtraction number sentences can be used to show comparison subtraction situations.
  • Finding a missing part of a whole is one interpretation of subtraction. Subtraction number sentences can be used to show missing part subtraction situations.
  • There are different interpretations of subtraction. Subtraction number sentences can be used to show each interpretation.
  • Addition and subtraction have an inverse relationship. The inverse relationship between addition and subtraction can be used to find subtraction facts; every subtraction fact has a related addition fact.
  • The difference can be written at the beginning or end of a subtraction sentence, as long as the number or expression on each side of the equal sign are the same amount.
  • Some problems can be solved by using objects to act out the actions in the problem.


Vocabulary:
missing part, subtract, difference, subtraction sentence, minus sign, equal sign, take away, compare, same amount


Students will be skilled at...


  • Solving problems by finding the missing part.
  • Finding a missing part of 8 when one part is known.
  • Using subtraction to find the missing part of 9 when one part is known.
  • Writing and solving subtraction number sentences.
  • Telling and acting out stories about taking away to find how many are left.
  • Telling and acting out comparing stories to find out how two groups are different.
  • Finding the missing part when one part and the whole are given.
  • Writing subtraction sentences to represent different kinds of subtraction stories.
  • Writing related addition and subtraction facts.
  • Writing and identifying different subtraction sentences that are true for the same model.
  • Using counters to act out and solve subtraction story problems.

Assessment Evidence

Performance Assessment:

Other Evidence:

Formative Assessments:



Learning Plan

Learning Activities:

  • 2-1 A missing part of a whole can be found when the whole and the other part are known.
  • 2-2 A missing part of a whole can be found when the whole and the other part are known.
  • 2-3 A missing part of a whole can be found when the whole and the other part are known.
  • 2-4 A missing part of a whole is one interpretation of subtraction. Subtraction number sentences can be used to show a missing part subtraction situation.
  • 2-5 Taking away parts from a whole is one interpretation of subtraction. Subtraction number sentences can be used to show taking-away subtraction situations.
  • 2-6 Comparing two quantities to find out how much more/less one quantity is than the other is one interpretation of subtraction. Subtraction number sentences can be used to show comparison subtraction situations.
  • 2-7 Finding a missing part of a whole is one interpretation of subtraction. Subtraction number sentences can be used to show missing part subtraction situations.
  • 2-8 There are different interpretations of subtraction. Subtraction number sentences can be used to show each interpretation.
  • 2-9 Addition and subtraction have an inverse relationship. The inverse relationship between addition and subtraction can be used to find subtraction facts; every subtraction fact has a related addition fact.
  • 2-10 The difference can be written at the beginning or end of a subtraction sentence, as long as the number or expression on each side of the equal sign are the same amount.
  • 2-11 Some problems can be solved by using objects to act out the actions in the problem.
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