Adding and Subtracting Within 1,000

Lesson 11

Math

Unit 5

2nd Grade

Lesson 11 of 25

Objective


Mentally subtract 10 and 100 from numbers within 1,000.

Student-Facing

I can mentally subtract 10 and 100 from numbers within 1,000.

Common Core Standards


Core Standards

  • 2.NBT.B.8 — Mentally add 10 or 100 to a given number 100—900, and mentally subtract 10 or 100 from a given number 100—900.

Foundational Standards

  • 1.NBT.B.2
  • 2.NBT.A.1
  • 2.NBT.A.2

Criteria for Success


  1. Count back by 10 or 100 to find the total.
  2. Know that when you subtract a ten the value of the tens place decreases or in some cases the value of the hundreds place will also decrease by one hundred. 
  3. Know that when you subtract a hundred the value of the hundreds place decreases by one hundred. 
  4. Relate standard form to unit form when subtracting 1 ten or 10 tens from a given number mentally. 

Tips for Teachers


Lesson Materials

  • Base ten blocks (10 hundreds, 18 tens, 18 ones per student)
  • Optional: Blank Hundreds Chart — Students can create a hundreds chart to 1,000 for reference

Warm Up

5-10 minutes


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Anchor Tasks

15-25 minutes


Problem 1

Build the number 168 with base ten blocks.

a.   Subtract 10. What is the difference?

b.   Subtract 100. What is the difference?

c.   In parts a and b, what digit changes? What digit(s) stay the same?

d.   Solve the following and think about what digits stay the same and which change.

  1. 343 - 100 = _____
  2. 343 - 10 = ______
  3. 713 - 100 = _____
  4. 594 - 10 = _____

Purpose

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Problem 2

Rahim says 100 - 10 is the same as 10 tens - 1 ten. 

a.   Do you agree with Rahim? Show your thinking. 

b.   Solve. 

  1. 200 - 10 = _____

  2. 304 - 10 = _____

  3. 807 - 10 = _____

  4. 900 - 10 = _____

c.   What do you notice about the differences?

Purpose

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Problem Set

15-20 minutes


Target Task

5-10 minutes


Use mental math to find the difference.

a.   873 - 10 = _____

b.   873 - 100 = _____

c.   500 - 10 = _____

d.   500 - 100 = _____

e.   43 tens - 1 ten = _____ The value is _____.

f.   78 tens - 10 tens = _____ The value is _____.

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

Subtract multiples of 10 and 100 from numbers within 1,000.

Lesson 12
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Lesson Map

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

Topic A: Adding with Mental Strategies

Topic B: Adding within 1,000

Topic C: Subtracting with Mental Strategies

Topic D: Subtracting within 1,000

Topic E: Story Problems and Explaining Addition and Subtracting Thinking

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