Lesson 8

How Many in the Bag

Est. Class Sessions: 2–3
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Mathematical Standards

1.OA.A
Represent and solve problems involving addition and subtraction. (1.OA.A.1, 1.OA.A.2)
1.OA.B
Understand and apply properties of operations and the relationship between addition and subtraction. (1.OA.B.3, 1.OA.B.4)
1.OA.C
Add and subtract within 20. (1.OA.C.6)
1.OA.D
Work with addition and subtraction equations. (1.OA.D.8)

Standards for Mathematical Practice

MP1.
Make sense of problems and persevere in solving them.
MP2.
Reason quantitatively.
MP5.
Use appropriate tools strategically.
MP6.
Attend to precision.

Students practice strategies for subtracting from larger numbers as they play the game How Many in the Bag. They discuss invented strategies used in the game, including using fact families to help solve subtraction problems.

Content in this Lesson

  • Representing subtraction using counters and number sentences [E2].
  • Solving separate/take away word problems involving two whole numbers whose sum is between 10 and 20 [E3].
  • Using mental math strategies and reasoning strategies (e.g., using doubles, using ten, making ten) to solve subtraction problems [E5, MPE2].
  • Using strategies that apply the properties of addition (e.g., turn-around, compose and decompose numbers) to solve subtraction problems [E6, MPE2].
  • Finding the unknown whole number in a subtraction sentence relating three whole numbers [E7].
  • Explaining reasoning orally and in writing [MPE5].
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Materials for Students

Daily Practice and Problems Lesson Homework Assessment

Student Book
Student Activity Book

Teacher Resources

 Teacher Guide - digital

Supplies for Students Pairs

paper bag, or opaque substitute
connecting cubes or other counters
desk number line (0–40)

Materials for the Teacher

Display of first page of How Many in the Bag (Student Activity Book) Page 409
Unit 12 Assessment Record
Math Facts Class Record
connecting cubes or counters
paper bag or opaque substitute
Invented Strategies chart from Lesson 1

Materials Preparation

Prepare Bags of Counters. Place 16 counters in a paper bag for class demonstration. Prepare a paper bag of 11–19 counters for each pair of students. Label the front of each bag with the number of counters in the bag.

Prepare Optional Targeted Practice. Customize and make copies of the Subtraction Circles Master to provide targeted practice with subtraction.

Assessment in this Lesson

Assessment Expectation Assessed Math Practices
Expectation Assessed

How Many in the Bag
Check-In: Question 2
Student Activity Book
Page 412
E2.
Represent addition and subtraction using stories, drawings, diagrams, counters, number sentences, number lines, or ten frames.
E3.
Solve word problems (e.g., join, separate/take away, part-whole, compare) involving two whole numbers whose sum is between 10 and 20.
E5.
Use mental math strategies and reasoning strategies (e.g., using doubles, using ten, making ten) to solve addition problems with sums between 10 and 20 and the related subtraction problems.
E6.
Use strategies that apply the properties of addition (e.g., turn-around, compose and decompose numbers) to solve addition and subtraction problems.
E7.
Find the unknown whole number in an addition or subtraction equation relating three whole numbers.
MPE2. 
Find a strategy. I choose good tools and an efficient strategy for solving the problem.
MPE5. 
Show my work. I show or tell how I arrived at my answer so someone else can understand my thinking.

DPP Item Y
 How Many
Teacher Guide - digital
E8.
Demonstrate fluency with the addition facts in Group A (0 + 1, 1 + 1, 2 + 1, 3 + 1, 0 + 2, 2 + 2, 3 + 2, 4 + 2).

DPP Item Z
Addition Facts Quiz: Group A
Teacher Guide - digital
E8.
Demonstrate fluency with the addition facts in Group A (0 + 1, 1 + 1, 2 + 1, 3 + 1, 0 + 2, 2 + 2, 3 + 2, 4 + 2).

DPP Item AA
Fact Family Quiz: Group A
Teacher Guide - digital
E9.
Determine the unknown number in an addition or subtraction sentence relating three whole numbers for the facts in Group A. (Algebra 4)

Vocabulary in this Lesson