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Adding and Subtracting Within 20

Unit Plan

Adding and Subtracting Within 20

Objectives

Students will learn reasoning strategies for basic addition and subtraction facts, including student-initiated strategies. Students will learn computation strategies based on flexible use of tens and number facts, including student-initiated strategies. Students will:

  • use their understanding of number combinations to develop fluency in the use of basic facts for addition and subtraction.
  • develop and use strategies for solving simple story problems.
  • develop and use strategies for whole-number computation with a focus on addition and subtraction of one- and two-digit numbers, with and without regrouping.
  • use a variety of methods and tools to compute and estimate sums and differences of quantities and conclude the reasonableness of the result.

Essential Questions

How are relationships represented mathematically?
How can expressions, equations, and inequalities be used to quantify, solve, model, and/or analyze mathematical situations?
How can mathematics support effective communication?
How can recognizing repetition or regularity assist in solving problems more efficiently?
How is mathematics used to quantify, compare, represent, and model numbers?
  • How is mathematics used to quantify, compare, represent, and model numbers?
  • How can expressions, equations, and inequalities be used to quantify, solve, model and/or analyze mathematical situations?

Related Unit and Lesson Plans

Related Materials & Resources

The possible inclusion of commercial websites below is not an implied endorsement of their products, which are not free, and are not required for this lesson plan.


Formative Assessment

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    Short-Answer Items

    1. Draw a line to match each number combination to its sum:

     

     

    5 + 8                                                  17

     

    4 + 7                                                  14

     

    8 + 9                                                  11

     

    6 + 8                                                  13

     

    2. List four number combinations that make 16:

     

     

    3. Draw a set of base-ten blocks that is 15 more than 28.

     


                > 28

     

     

     

     

     

     

    For questions 4 and 5, write <, >, or = in the large box to make the sentence true.

     

     

     

    4.      

     

     

     

     

     

     

     

     

     

    5.

     

     


    For questions 6, 7, and 8, fill in the missing numbers. Use blocks to help you.

     

     

    6.

                    

     

     

    7.

                    

     

     

    8.

                    

     

     

     

    9.       Write a different number sentence using the same numbers as are in the number sentence below.

     

    94 − 27 = 67

     

     

     

     

     

     

    10. Tom had 37 baseball cards. He bought 25 more. How many baseball cards does Tom have?

    Show all your work.

     

     

    11. Sue had 85 gumballs in her gumball machine. She gave out 48 of the gumballs. How many gumballs are still in Sue’s gumball
    machine?

    Show all your work.

     

     

     

     

     

     

     

    12. Seth ate 12 jelly beans from a candy jar. There are still 29 jelly beans in the jar. How many jelly beans were in the candy jar before Seth started eating them?

    Show all your work.

     

     

    Short-Answer Key and Scoring Rubric:

     

    1. Draw a line to match each number combination to its sum:

     

     

     

     

    2. List four number combinations that make 16:

     

    Answers will vary, but will include any 4 of the following:

             0 + 16, 1 + 15, 2 + 14, 3 + 13, 4 + 12, 5 + 11, 6 + 10, 7 + 9, 8 + 8

     

     

     

    3. Draw a set of base-ten blocks that is 15 more than 28.

     

     

    For questions 4 and 5, write <, >, or = in the large box to make the sentence true.

     

    4.     

     

     

     

    5.

     

     

     

    For questions 6, 7 and 8, fill in the missing numbers. Use blocks to help you.

     

    6. 

     

            

            

    7.

         

              

    8.

                    

     

     

    9. Write a different number sentence using the same numbers as are in the number sentence below.

     

    94 − 27 = 67

    67 + 27 = 94 or 27 + 67 = 94 or 94 − 67 = 27

     

    10. Tom had 37 baseball cards. He bought 25 more. How many baseball cards does Tom have?

     

    Show all your work.

    Tom has 62 baseball cards.

    Work will vary.

     

    11. Sue had 85 gumballs in her gumball machine. She gave out 48 of the gumballs. How many gumballs are still in Sue’s gumball machine?

     

    Show all your work.

    37 gumballs are still in Sue’s gumball machine.

    Work will vary.

     

    12. Seth ate 12 jelly beans from a candy jar. There are still 29 jelly beans in the jar. How many jelly beans were in the candy jar before Seth started eating them?

     

    Show all your work.

    41 jelly beans were in the jar before Seth started eating them.

    Work will vary

     

    Scoring Rubric for Questions 10, 11, and 12.

     

    Points

    Description

    2

    • Written explanation is thorough, clear, and supported with visual representation.
    • Student shows complete understanding of the mathematics.
    • Answer is correct.
    • Student meets the requirements of the problem.

    1

    • Written explanation is brief and is partly supported by the visual representation.
    • Student shows partial understanding of the mathematics.
    • Answer is incorrect due to a minor mathematical error.
    • Student partially meets the requirements of the problem.

    0

    • Written explanation is brief or missing and there is no visual representation.
    • Student shows no understanding of the mathematics.
    • Answer is incorrect due to a major mathematical error/misunderstanding or is missing.
    • Student does not meet the requirements of the problem.

    Performance Assessment:

    Rowland has 100 pennies. He put them into two separate piles.

     

    1. He put 50 pennies in one pile. How many pennies are in the other pile?

     

     

     

     

     

    2.  He takes 4 pennies from the pile of 50 and moves them to the other pile. How many pennies are in each pile now?

     

     

    3. Write a number sentence to show the number of pennies in each pile.

     

     

     

     

     

    4.  Rowland puts all the pennies together again and starts over. He puts 73 pennies in one pile. How many pennies are left for the other pile?

     

     

    5. Write a number sentence to show the number of pennies in each pile.

     

     

     

    6. Write a subtraction number sentence to show the solution for problem 4.

     

    7.    Write 5 different number sentences showing different ways to use addition to make 100.

     

     

     

     

     

     

     

     

     

    8. Write 5 different number sentences that show subtracting a number from 100.

     

    Performance Assessment Key and Scoring Rubric:

    Rowland has 100 pennies. He put them into two separate piles.

    1. He put 50 pennies in one pile. How many pennies are in the other pile? 50
    2. He takes 4 pennies from the pile of 50 and moves them to the other pile. How many pennies are in each pile now? 46 & 54
    3. Write a number sentence to show the number of pennies in each pile.

    50 − 4 = 46 & 50 + 4 = 54

    or  46 + 54 = 100 or 54 + 46 = 100

    1. Rowland puts all the pennies together again and starts over. He puts 73 pennies in one pile. How many pennies are left for the other pile? 27
    2. Write a number sentence to show the number of pennies in each pile and their total.

     

    73 + 27 = 100 or 27 + 73 = 100

     

    1. Write a subtraction number sentence to show the solution for problem 4.

     

    100 − 73 = 27

     

    1. Write 5 different number sentences showing different ways to use addition to make 100. Answers will vary.
    2. Write 5 different number sentences that show subtracting a number from 100.
      Answers will vary.

     

     

     

     

     

     

     

     

     

     

     

    Points

    Description

    4

    • Mathematics is correct with complete work shown.
    • Written explanations are thorough, detailed, and clear.
    • Student displays excellent understanding of the questions, mathematical concepts, and processes.
    • Student performs beyond the problem requirements, possibly incorporating multiple methods/solutions.
    • Pictorial representation is appropriate, of excellent quality, and creative.

    3

    • Mathematics is correct with work shown.
    • Written explanations are thorough and clear.
    • Student displays good understanding of the questions, mathematical concepts, and processes.
    • Student meets all problem requirements.
    • Pictorial representation is appropriate, of good quality, and neat.

    2

    • Mathematics is correct with minimal or no work shown.
    • Written explanations are present but lacking some detail.
    • Student displays partial understanding of the questions, mathematical concepts, and processes.
    • Student meets most of the problem requirements.
    • Pictorial representation is complete but may have errors.

    1

    • Mathematics is incorrect with some work shown.
    • Written explanations are incomplete and lack detail.
    • Student displays little understanding of the questions, mathematical concepts, and processes.
    • Student does not meet a majority of the requirements of the problem.
    • Pictorial representation is incomplete, inappropriate for the situation, or missing.

    0

    • Mathematics is incorrect with no work shown.
    • Written explanations are illogical or not present.
    • Student displays no understanding of the questions, mathematical concepts, and processes.
    • Student does not meet the requirements of the problem.
    • Pictorial representation is missing.
Final 4/29/14
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