Curriculum  /  Math  /  2nd Grade  /  Unit 2: Adding and Subtracting Within 100  /  Lesson 11

Adding and Subtracting Within 100

Lesson 11

Math

Unit 2

2nd Grade

Lesson 11 of 21

Objective

Use place value knowledge to subtract with one decomposition.

Student-Facing

I can exchange a ten for 10 ones to subtract.

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.

Foundational Standards

  • 1.NBT.C.4
  • 1.NBT.C.5
  • 1.NBT.C.6

Criteria for Success

  1. Represent the minuend using place value drawings to show tens and ones. 
  2. When necessary, decompose a ten into 10 ones and redraw the number as an equivalent value with more than 10 ones (for example 42 would be represented as 3 tens, 12 ones). 
  3. Subtract the subtrahend by taking away ones and then tens appropriately.

Tips for Teachers

In first grade, students decomposed a ten to make 10 ones when subtracting one-digit numbers from two-digit numbers. Here, they will be making the decomposition and also accounting for subtracting tens as well. A common miscalculation to look out for is when students subtract but without taking into account the new tens. 

Lesson Materials

  • Base ten blocks — teacher set 3 tens and 20 ones

Warm Up

5-10 minutes

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Anchor Tasks

15-25 minutes

Problem 1

Josh has blocks that represent 30 in the form of 3 tens blocks. He needs to give 15 to his math partner. How can he make this exchange?

Purpose

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Set Up

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Problem 2

a.   Rewrite the following numbers. 

  1. _____ = 2 tens + 14 ones
  2. 41 = 3 tens + _____ ones
  3. 65 = 5 tens + _____ ones
  4. _____ = 4 tens + 10 ones

b.   Select two numbers from part a and show how you would subtract 28. 

 

Purpose

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Problem 3

Model with a place value chart to subtract. 

a.   40 - 19 = 

b.   33 - 24 = 

c.   72 - 25 = 

d.   60 - 27 = 

Purpose

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Problem Set

15-20 minutes

Target Task

5-10 minutes

Model with a place value chart to solve. 

a.   42 - 23 = _____ 

b.   90 - 32 = _____

c.   88 - 19 = _____

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

Use properties of operations to subtract within 100.

Lesson 12
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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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