Addition and Subtraction of Fractions/Decimals

Lesson 14

Objective

Subtract decimals.

Materials and Resources

Common Core Standards

Core Standards

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  • 5.NBT.B.7 — Add, subtract, multiply, and divide decimals to hundredths, 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.

Foundational Standards

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  • 5.NBT.A.1

  • 5.NBT.A.4

  • 4.NF.C.5

Criteria for Success

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  1. Understand that in order to subtract quantities, they must have the same unit (which in the case of decimals, are their place values). 
  2. Subtract like units with decimals using an area model or the standard algorithm, aligning place values correctly (which results in the decimal points being aligned) (MP.5, MP.6). 
  3. Estimate differences of decimals. 
  4. Use the relationship between addition and subtraction to check the solution to a decimal subtraction problem (MP.7). 
  5. Solve one-step word problems involving the subtraction of two decimals (MP.4).

Tips for Teachers

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As a supplement to the Problem Set, students could play "Race to Zero Decimal Spinner" from 5.NBT.7 - About the Math, Learning Targets, and Rigor by the Howard County Public School System.

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Anchor Tasks

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Problem 1

  1. Solve. 
    1. 3 eighths – 1 fourth = ___________
    2. 3 fifths – 1 half = ___________
    3. 3 tenths – 1 hundredth = ___________
  2. What do you notice about #1 above? What do you wonder?

Guiding Questions

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Problem 2

Solve. Show your work with an area model.

  1.  0.8 – 0.2 
  2.  0.94 – 0.6
  3.  0.7 – 0.13

Guiding Questions

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Problem 3

Solve. Show your work. Then use addition to check your work. 

a.    12.72 – 5.95 

b.    8 – 0.34

Guiding Questions

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References

EngageNY Mathematics Grade 5 Mathematics > Module 1 > Topic D > Lesson 10Concept Development

Grade 5 Mathematics > Module 1 > Topic D > Lesson 10 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

Modified by The Match Foundation, Inc.

Problem 4

  1. Estimate the following differences. 
    1.   5.194 – 3.76
    2.   73.73 – 41.123
  2. Solve for the actual differences in #1 above. Are your answers reasonable? Why or why not?

Guiding Questions

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Discussion of Problem Set

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  • Look at #2d. I wasn’t able to subtract since 10 has no tenths or hundredths. Do you agree or disagree? 
  • Look at #3. Was Michael correct? What error did he make? 
  • Look at #4. Was Peter correct? How can you prove him wrong without calculating the actual difference? 
  • Look at #8. Who thinks they have the smallest difference? Did anyone get a smaller difference? What was your strategy?

Target Task

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Solve. 

  1.    84.37 – 28.6 = __________
  2.    7 – 0.35 = __________

References

EngageNY Mathematics Grade 5 Mathematics > Module 1 > Topic D > Lesson 10Exit Ticket, Question #2

Grade 5 Mathematics > Module 1 > Topic D > Lesson 10 of the New York State Common Core Mathematics Curriculum from EngageNY and Great Minds. © 2015 Great Minds. Licensed by EngageNY of the New York State Education Department under the CC BY-NC-SA 3.0 US license. Accessed Dec. 2, 2016, 5:15 p.m..

Modified by The Match Foundation, Inc.

Mastery Response

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