Curriculum  /  Math  /  2nd Grade  /  Unit 2: Adding and Subtracting Within 100  /  Lesson 14

Adding and Subtracting Within 100

Lesson 14

Math

Unit 2

2nd Grade

Lesson 14 of 21

Objective

Relate subtraction with place value drawings to the standard algorithm in situations with one decomposition and explain thinking.

Student-Facing

I can record my subtraction thinking vertically to subtract when there aren't enough ones.

Common Core Standards

Core Standards

  • 2.NBT.B.5 — Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
  • 2.NBT.B.9 — Explain why addition and subtraction strategies work, using place value and the properties of operations. Explanations may be supported by drawings or objects.

Foundational Standards

  • 1.NBT.C.4
  • 1.NBT.C.5
  • 1.NBT.C.6
  • 1.OA.B.3
  • 1.OA.B.4

Criteria for Success

  1. Represent or draw the minuend in a given subtraction situation with a place value drawing and show the equation in a vertical model with numbers aligned by place value. 
  2. Show subtraction by decomposing a ten into 10 ones to take away the ones and tens of the subtrahend in the place value drawing.

Tips for Teachers

In this lesson, students encounter subtraction problems where they need to decompose a ten into 10 ones in order to subtract. When showing this vertically, students should cross out the ones and rewrite it as the new teen-numbered ones so that students internalize that they are not adding 1 but adding 10 ones. See the Student Responses for examples of what this looks like.

Warm Up

5-10 minutes

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Anchor Tasks

15-25 minutes

Problem 1

Charlie tried to model the problem 53 - 17, but realized there weren't enough ones to subtract. 

Help Charlie model the subtraction problem using a place value chart. Record your thinking vertically. What should Charlie do to subtract? Explain how you solve.

Purpose

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Problem 2

Model subtracting using a place value chart. Record your thinking vertically. 

a.   62 - 25 =______ 

b.   70 - 34 =______

c.   81 - 44 =______

d.   100 - 69 =______

Purpose

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Problem 3

Model both problems using a place value chart. Record your thinking vertically. 

65 - 43 =

65 - 38 =

Explain how the two problems are different to solve. 

Purpose

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Problem Set

15-20 minutes

Target Task

5-10 minutes

Model subtracting using a place value chart. Record your thinking vertically. 

73 - 16 = ______

Explain, did you have to decompose a ten to solve? Why or why not?

Student Response

Additional Practice

Daily Word Problems, Warm Ups, and Center Activities are aligned to the content of the unit but not necessarily to the lesson objective, therefore feel free to use them anytime during your school day.

Word Problems and Fluency Activities

Next

Represent and solve compare story problems within 100 (Day 1).

Lesson 15
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Lesson Map

A7CB09C2-D12F-4F55-80DB-37298FF0A765

Topic A: Adding & Subtracting with Multiples of Ten

Topic B: Strategies for Adding within 100

Topic C: Strategies for Subtracting within 100

Topic D: Working within 100 and Categorical Data

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