Chapter 8

Addition & Subtraction Facts to 20

1st Grade: Chapter 8 Outline

Week 17 - Week 18

Essential Questions:

    • What strategy would be appropriate addition and subtraction problems?
    • Can you add and subtract fluently?
    • How do I write a fact family from a given number sentence?
    • What strategies can I use to make addition or subtraction easier?
    • What strategies can I use to find the unknown number in an equation?
    • How can I use this skill to solve problems?
    • How can drawing a picture and writing a number sentence help you solve subtraction problems?
    • How can counting on or counting back help me to subtract?

Content:

Students will know and understand:

    • addition and Subtraction.
    • sum.
    • fact Families- Commutative and Associative Properties.
    • properties of operation strategies.
    • order (first, second).
    • the relationship between addition and subtraction.

Skills:

Students Will:

    • relate counting on to adding counting all, counting on, and counting back.
    • use mathematical tools and representations
    • use properties and strategies to solve addition and subtraction problems within 20.
    • find the unknown number in an addition or subtraction equation relating two whole numbers whose sum is less than 20.
    • know the relationship between addition and subtraction within 20.
    • use various strategies to solve subtraction problems.

Upon completion of Unit 8:

  • 1.OA.A.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.A.2. Solve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
  • 1.OA.B.4. Understand subtraction as an unknown-addend problem.
  • 1.OA.C.6. Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use 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.D.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.
  • 1.OA.D.8. Determine the unknown whole number in an addition or subtraction equation relating to three whole numbers.
  • 1.NBT.C.4. Add within 100, including adding a two-digit number and a one-digit number, and adding a two-digit number and a multiple of 10, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used. Understand that in adding two-digit numbers, one adds tens and tens, ones and ones; and sometimes it is necessary to compose a ten.
  • MP.1. Make sense of problems and persevere in solving them.
  • MP.2. Reason abstractly and quantitatively.
  • MP.3. Construct viable arguments and critique the reasoning of others.
  • MP.4. Model with mathematics.
  • MP.6. Attend to precision.
  • MP.8. Look for and express regularity in repeated reasoning.