Writing Subtraction Number Sentences

Understanding Addition and Subtraction

instruction

 

Click on the link below to watch the animation.

Web Link Button  Subtraction: Writing Subtraction Number Sentences

 

Click on the link below to print and use the Part-Part-Whole Mat to complete the activities with your Learning Coach.

Web Link Button Part-Part-Whole Mat


Read 
Read pages 12–13 in enVisionMATH 2 with your Learning Coach.


Discuss  Write 
Discuss and complete the Guided Practice problems on page 12, #1–4 with your Learning Coach.


Write 
Complete the Independent Practice problems on pages 13–14, #5–10.


Click on the link below to view a PDF sample of the iText pages you need for this lesson.

IText button  enVisionMATH 2


Lesson Guide

Click on the link below to print and use the Part-Part-Whole Math to complete the activities with your student.

mouse4  Part-Part-Whole Mat


Academic Vocabulary
Write 5 – 3 = 2 on a piece of paper. This is a subtraction sentence.  What does this symbol mean? Circle the minus sign. The minus (–)  sign tells you that one of the parts, 3, is being taken away from the whole, 5. When you subtract, you find the missing part, or the difference.

Pose the Problem
Give your student a paper bag with 8 cubes and a Part-Part-Whole Mat. Have him take 2 cubes out of his bag. How can you use the mat to show how many cubes are still in the bag? What number would you write at the top of the mat? Allow time for your student to work with his cubes and mat and share his answer.
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Interaction
Open the student text to page 11. Lead your student to recognize that he is working with one part and the whole, and that he needs to find the missing part. How many cubes did I place in the bag? [ 8] I took out 2 cubes. What do you need to find? [ Sample responses: the missing part; the number of cubes still in the bag; the other part] 8 is the whole. Have your student write "8" in the whole box at the top of the mat. Explain that he can place the cubes for the part he knows [ 2] on one side of the mat.  2 is one of the parts. The missing part is the number of cubes still in the bag. Guide your student to fill in each part of Item 1. Have your student place the 8 connecting cubes back in the bag. Then guide him to repeat this activity and use the Part-Part-Whole Mat to find the number of cubes remaining in the bag and complete the subtraction sentences for Items 2 and 3. 
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Guided Practice
Read pages 12–13 with your student.
Alternatively, you may view the animation with your student and answer any questions he may have.
Have your student discuss and complete the Guided Practice problems on page 12, #1–4 with you.

Tips

  • Remind your student that the number that appears in the box at the top is always the whole in the subtraction sentence.
  • Your student may not understand that the whole minus the part equals the missing part. Have him use a Part-Part-Whole Mat, number cards, and cubes.
  • Exercise 2
    If your student has difficulty understanding that the whole is made up of the part he sees and the missing part, then have him use connecting cubes to model the operation.

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Independent Practice

Have your student complete the Independent Practice problems on pages 13–14, #5–10.

Tips

  • Encourage your student to use counters to help him model and solve the subtraction sentences.
  • Exercise 8
    Use Part-Part-Whole Models  Use a part-part-whole model to represent the problem situation. How many marbles does Rita have in her box to begin with? [ 12] How many marbles does she take out of the box? [ 7] What can you do to find out how many marbles are left in the box? [ Subtract]
  • Exercise 9
    Test-Taking Tip: Understand the Question  Encourage your student to think about what he needs to find in order to answer the question. You need to find out how many children are still playing the game after 3 have gone home.  

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