Addition and Subtraction of Fractions/Decimals

Lesson 13

Objective

Add 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 add quantities, they must have the same unit (which in the case of decimals, are their place values). 
  2. Add 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 sums of decimals. 
  4. Understand that the commutative and associative properties still hold with decimal addition (MP.7). 
  5. Solve one-step word problems involving the addition of two decimals (MP.4).

Tips for Teachers

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As a supplement to the Problem Set, students can solve the puzzle "Decimal Addition Puzzle" from 5.NBT.7 - About the Math, Learning Tasks, 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.

a.    0.3 + 0.5

b.    0.64 + 0.7

Guiding Questions

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Problem 3

Solve. Show your work.

a.    3.37 + 10.64

b.    0.7 + 15

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Problem 4

  1. Estimate the following sums. 
    1. 3.419 + 2.67
    2. 4.99 + 56.123 +123.01 + 3.7
  2. Solve for the actual sums 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. If someone got 64 as an answer, how would you explain to them that their answer is unreasonable? 
  • Look at #3. Is Jeremy’s answer reasonable? How do you know? What mistake did he make? 
  • Look at #4. Did anyone solve without actually adding any values together? How were you able to do that? 
  • Look at #5. When I added, I got 16.00, but I don’t see that as an option. What mistake did I make? 
  • Look at #7. Why does this strategy work? When might it be helpful to use?
  • Look at #8. Who thinks they have the smallest sum? Did anyone get a smaller sum? What was your strategy?

Target Task

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Solve. 

1.      2.40 + 1.8 = __________

2.      36.25 + 8.67 = __________

References

EngageNY Mathematics Grade 5 Mathematics > Module 1 > Topic D > Lesson 9Exit Ticket, Question #2

Grade 5 Mathematics > Module 1 > Topic D > Lesson 9 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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